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    <entry>
      <title>2020年度总结</title>
      <link href="/2020/12/31/2020-nian-du-zong-jie/"/>
      <url>/2020/12/31/2020-nian-du-zong-jie/</url>
      
        <content type="html"><![CDATA[<h1 id="2020年度总结"><a href="#2020年度总结" class="headerlink" title="2020年度总结"></a>2020年度总结</h1><blockquote><p>突发奇想写的这篇文章，并没有细细构思，只是回忆一下2020年菜鸡豪做的事情，顺带整理一下回忆继续出发，奔向崭新的2021！<strong>我们都是努力奔跑的追梦人！</strong></p></blockquote><h2 id="一月"><a href="#一月" class="headerlink" title="一月"></a>一月</h2><p>其实现在回想一月发生的事情，脑海里只存留着几个断断续续的片段，但是我清楚的记得我的新年愿望：</p><p>“<strong>能够比19年更努力，更幸运。</strong>”</p><p><a href="https://imgchr.com/i/rjzuWj" target="_blank" rel="noopener"><img src="https://s3.ax1x.com/2020/12/31/rjzuWj.md.png" alt="rjzuWj.md.png"></a></p><p>当然这个目标没有限定的界限，我说它实现了，那它就是实现了；我说它没有实现，那它就是没有实现。之所以定这么一个模糊的目标，是因为我不想失望了。至少我心里知道，比起整个19，我确实更加努力了，掌握了一些技能，也明白了一些道理。至于幸运，也算是挺幸运的吧。</p><p><strong>总有一些误解，不去了解，是不会解开的！</strong>很多时候我们总是会主观臆断，从自己主观的角度去理解问题，不会明白别人是怎么想的。不过这都是人之常情，所谓<em>人不为己，天诛地灭。</em>确实是这样的，因为大家都是普通人。所以有时候真的需要冷静下来了解一下让你烦恼的事情，然后就会发现，有些事情，看似偶然，实则必然。</p><p>还有就是，确实是有点可惜，来中北三年了，连一场像样的大学都没有见到过，北方的冬天真是这样子吗？很明显不是的，回家以后我就见到了真正的冬天，放眼望去，整个大地都是白的，那种久违的感觉着实Nice。再有就是在1月底看到偶像<strong>科比</strong>坠机事件，当时第一感觉就是：“卧槽，假的吧！！”然而事实就是如此，不接受也没办法。</p><h2 id="二-三月"><a href="#二-三月" class="headerlink" title="二/三月"></a>二/三月</h2><p>这两个月对我来说过的十分平凡，但对中国来说非常不平凡，也就是老生常谈的新馆疫情，现在想想好像也就那么回事，但是真正经历的时候确实感受很深，小区不让出，街上每天都有交警巡逻，为了大家的生命安全，白衣天使们义不容辞的奔向战场，好像据说年龄比我也大不了几岁，当时的笔者热血沸腾，但是现在想想都是故事。当时，有程序员自发的在网站上面收集整理疫情信息，我有关注，还加了一个微信群，群里每天都会有人发一些疫情信息，并在<strong>GitHub</strong>上进行同步整理。</p><p>大概是从三月份开始的吧，我每天早上都会和铁子去公园跑步，跑的不咋快，确挺快乐，其实我们还坚持了蛮久的，哈哈哈哈，不过自从铁子回学校以后我就开始堕落了，那个时候我才知道什么两周定律都是假的，唯一的敌人就是心中的欲望，而要做的就是满足心中的欲望，战胜自己，好的上战胜任何敌人：这也是为什么<strong>“我不是想赢，我只是不想输”</strong>，大概大家都是这么想的吧。</p><p><a href="https://imgchr.com/i/rvkCrj" target="_blank" rel="noopener"><img src="https://s3.ax1x.com/2020/12/31/rvkCrj.md.jpg" alt="rvkCrj.md.jpg"></a></p><h2 id="四-五月份"><a href="#四-五月份" class="headerlink" title="四/五月份"></a>四/五月份</h2><p>这个时候应该是上网课的时候了吧，可能这辈子都不会想到，竟然会有一天，真的可以坐在家里上课，听着老师在电脑上讲的那些知识，什么寄存器了，什么OSI了，听着听着，我好困啊，直接就睡了。哈哈，再家确实666，在家呆的想回学校也是没谁了，那应该是最长的一个寒假了，直接寒暑假一起过了，如果不是还有几个比赛一直在催着我学点东西，那我可能真的挂了。</p><p>这个时候的考试就更不用说了，哈哈哈哈，大家懂的都懂，有考好的，就有考差的，我就属于后者，其实我觉得大学的考试真的不能说明一个人的专业水平，因为老师们经常说考试是通过性考试，目的就是让大家通过。如果真正做过项目的话就应该知道，在课上学的那点点皮毛的知识远远不够，不是说课上的东西不重要，而是说要学的东西远远比课上学的那点要多得多，很多知识，需要在自己摸索中去寻找规律，我发现，其实生活中的好多东西都是相同的，大家都能够理解的，这就是为什么大家都是普通人。</p><p>网课大概就是这个样子，我不知道大家的单片机费了没有，反正我是废了，我就是个废物。</p><h2 id="六-七-八月份"><a href="#六-七-八月份" class="headerlink" title="六/七/八月份"></a>六/七/八月份</h2><p>这几个月份，应该是连着暑假了吧，暑假有一个社会实践，我就是在本地找了一份兼职，每天的任务也很简单，就是擦车，在亲戚家的一个洗车厂做了大概有快一个月吧，给我的感觉就是，这大概就是普通人每天的生活吧，其实想想，如果能够在这样一个城市，办一个店铺，自己做一点自己喜欢的事情，每天有喜欢的人，偶尔碰到烦心的事情，这样的养老生活也是十分惬意的。之所以说是养老生活是因为我觉得，趁年轻还是应该出去闯一闯，长长见识，了解世界的多姿多彩，就能够了解自己的渺小。</p><p>除了暑假社会实践，我剩下的任务应该就是两个比赛了，一个计设，一个互联网+，都说自己决定不了一生的贵人相助，我很感谢那些曾经给我帮助的人，但无以为报。有很多矫情的话，大家懂的都懂。今年的计设可以说是对我的成长比较大，对我的整个的人格成长也起到了至关重要的作用，让我明白了这个世界上，有些东西，只要你努力去做了，结果总不会太差。我们的作品是<strong>《检路》</strong>，也在比赛中取得了比较好的名次。</p><p><a href="https://imgchr.com/i/rvEVvF" target="_blank" rel="noopener"><img src="https://s3.ax1x.com/2020/12/31/rvEVvF.png" alt="rvEVvF.png"></a></p><p><a href="https://imgchr.com/i/rvEKER" target="_blank" rel="noopener"><img src="https://s3.ax1x.com/2020/12/31/rvEKER.jpg" alt="rvEKER.jpg"></a></p><p>名字就不打码了，哈哈哈哈哈。</p><h2 id="九月"><a href="#九月" class="headerlink" title="九月"></a>九月</h2><p>这个时候应该是开学了，开学就意味着有一堆的事情要做，据说大三上是物联网专业最忙的一个学期，现在想想好像这确实是真的，交不完的实验报告，计科都考完试了我们还没结课，当然这都是后话，金工实习也是比较开心的一件事情，不过确实蛮累的，到现在都依稀能想起钢锯在我耳边响的声音，都是一种经历吧。这个学期真的累成狗。</p><h2 id="十-十一月"><a href="#十-十一月" class="headerlink" title="十/十一月"></a>十/十一月</h2><p>这两个月是课最多的时候，物联网最苦的时候大概就是，一次要交十几分实验报告，要求是先打印出来，然后手写，然后在一张一张的拍照，然后再把图片放在word文件中弄成电子版上传。这是我见过最6的交作业的方式，简直不要太好了，哈哈哈哈。这学期光实验报告就打了很多很多，都是money啊。</p><h2 id="十二月"><a href="#十二月" class="headerlink" title="十二月"></a>十二月</h2><p>这个月也是魔鬼的一个月，分分分，学生的命根。不知道大家有没有听过这样一句话，<strong>内卷没有上限</strong>。这是今年才出来的，我的感受是比较深的，懂的都懂。大家都在以自己的方式努力着，我也一样，我也不知道我还能走多远，也不知道能到达一个什么样的高度，但是或许就是这样的未知数，才更让人向往。</p><p>这个月有一个彩蛋，在2020年12月21号，我党正式接收我为中共预备党员，从此，笔者必将更加努力，更加用工，尽自己的努力做自己力所能及的事情。</p><p>今天是2020年的最后一天了，保不齐明天就要被消灭了。</p><p><code>2021的目标：</code>希望自己能够更加努力，更加幸运。</p><p><strong>最后结尾：</strong>渐渐明白一些道理，也就没有什么很想维持的关系了，来着不拒，走者不留！当时光流逝，兜兜转转……</p>]]></content>
      
      
      
        <tags>
            
            <tag> 杂记 </tag>
            
        </tags>
      
    </entry>
    
    
    
    <entry>
      <title>20年安卓暑期考核算法题</title>
      <link href="/2020/08/08/20-nian-an-zhuo-shu-qi-kao-he-suan-fa-ti/"/>
      <url>/2020/08/08/20-nian-an-zhuo-shu-qi-kao-he-suan-fa-ti/</url>
      
        <content type="html"><![CDATA[<p>[TOC]</p><h1 id="20年安卓暑期考核算法题"><a href="#20年安卓暑期考核算法题" class="headerlink" title="20年安卓暑期考核算法题"></a>20年安卓暑期考核算法题</h1><h2 id="一：缺失数字"><a href="#一：缺失数字" class="headerlink" title="一：缺失数字"></a>一：缺失数字</h2><h3 id="题目描述"><a href="#题目描述" class="headerlink" title="题目描述"></a>题目描述</h3><blockquote><p> 给定一个包含 <code>0, 1, 2, ..., n</code> 中 <em>n</em> 个数的序列，找出 0 .. <em>n</em> 中没有出现在序列中的那个数。 </p></blockquote><h3 id="解题思路"><a href="#解题思路" class="headerlink" title="解题思路"></a>解题思路</h3><blockquote><p>将给定数列排序，然后使用for循环依次进行比对，比对结果不匹配的数字即为所求。</p></blockquote><h3 id="Java代码"><a href="#Java代码" class="headerlink" title="Java代码"></a>Java代码</h3><pre class=" language-java"><code class="language-java"><span class="token keyword">class</span> <span class="token class-name">Solution</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">int</span> <span class="token function">missingNumber</span><span class="token punctuation">(</span><span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> nums<span class="token punctuation">)</span> <span class="token punctuation">{</span>        Arrays<span class="token punctuation">.</span><span class="token function">sort</span><span class="token punctuation">(</span>nums<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">//排序操作</span>        <span class="token keyword">for</span><span class="token punctuation">(</span><span class="token keyword">int</span> i<span class="token operator">=</span><span class="token number">0</span><span class="token punctuation">;</span> i <span class="token operator">&lt;</span> nums<span class="token punctuation">.</span>length<span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span><span class="token punctuation">{</span>            <span class="token keyword">if</span><span class="token punctuation">(</span>nums<span class="token punctuation">[</span>i<span class="token punctuation">]</span> <span class="token operator">!=</span> i<span class="token punctuation">)</span>  <span class="token comment" spellcheck="true">//if判断</span>                <span class="token keyword">return</span> i<span class="token punctuation">;</span>        <span class="token punctuation">}</span>        <span class="token keyword">return</span> nums<span class="token punctuation">.</span>length<span class="token punctuation">;</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h3 id="python代码"><a href="#python代码" class="headerlink" title="python代码"></a>python代码</h3><pre class=" language-python"><code class="language-python"><span class="token keyword">class</span> <span class="token class-name">Solution</span><span class="token punctuation">:</span>    <span class="token keyword">def</span> <span class="token function">missingNumber</span><span class="token punctuation">(</span>self<span class="token punctuation">,</span> nums<span class="token punctuation">:</span> List<span class="token punctuation">[</span>int<span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token operator">-</span><span class="token operator">></span> int<span class="token punctuation">:</span>        <span class="token comment" spellcheck="true"># 排序</span>        nums<span class="token punctuation">.</span>sort<span class="token punctuation">(</span><span class="token punctuation">)</span>        <span class="token comment" spellcheck="true"># 使用for循环进行对比</span>        <span class="token keyword">for</span> i <span class="token keyword">in</span> range<span class="token punctuation">(</span>len<span class="token punctuation">(</span>nums<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">:</span>            <span class="token keyword">if</span> nums<span class="token punctuation">[</span>i<span class="token punctuation">]</span> <span class="token operator">!=</span> i<span class="token punctuation">:</span>                <span class="token keyword">return</span> i        <span class="token keyword">return</span> i<span class="token operator">+</span><span class="token number">1</span></code></pre><h2 id="二：字母异位词分组"><a href="#二：字母异位词分组" class="headerlink" title="二：字母异位词分组"></a>二：字母异位词分组</h2><h3 id="题目描述-1"><a href="#题目描述-1" class="headerlink" title="题目描述"></a>题目描述</h3><blockquote><p>给定一个字符串数组，将字母异位词组合在一起。字母异位词指字母相同，但排列不同的字符串。</p><p>示例:</p><p>输入: [“eat”, “tea”, “tan”, “ate”, “nat”, “bat”]<br>输出:<br>[<br>[“ate”,”eat”,”tea”],<br>[“nat”,”tan”],<br>[“bat”]<br>]<br>说明：</p><p>所有输入均为小写字母。<br>不考虑答案输出的顺序。</p></blockquote><h3 id="解决思路"><a href="#解决思路" class="headerlink" title="解决思路"></a>解决思路</h3><blockquote><p>将给定的字符串转换为数组，在将数组排序后重新转换为字符串然后进行比对，如果存在就放在一起，不存在就另起一行，使用HashMap建立映射关系，最终返回一个ArrayList。</p></blockquote><h3 id="Java代码-1"><a href="#Java代码-1" class="headerlink" title="Java代码"></a>Java代码</h3><pre class=" language-java"><code class="language-java"><span class="token keyword">class</span> <span class="token class-name">Solution</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> List<span class="token operator">&lt;</span>List<span class="token operator">&lt;</span>String<span class="token operator">>></span> <span class="token function">groupAnagrams</span><span class="token punctuation">(</span>String<span class="token punctuation">[</span><span class="token punctuation">]</span> strs<span class="token punctuation">)</span> <span class="token punctuation">{</span>        <span class="token comment" spellcheck="true">// 返回值为List类型，List里面嵌套List，数据为String类型，因此定义HashMap值为List</span>        Map<span class="token operator">&lt;</span>String<span class="token punctuation">,</span> List<span class="token operator">></span> map <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">HashMap</span><span class="token operator">&lt;</span>String<span class="token punctuation">,</span> List<span class="token operator">></span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>        <span class="token keyword">for</span> <span class="token punctuation">(</span>String i <span class="token operator">:</span> strs<span class="token punctuation">)</span><span class="token punctuation">{</span>            <span class="token comment" spellcheck="true">// 将字符串转换为数组</span>            <span class="token keyword">char</span><span class="token punctuation">[</span><span class="token punctuation">]</span> arr <span class="token operator">=</span> i<span class="token punctuation">.</span><span class="token function">toCharArray</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>            Arrays<span class="token punctuation">.</span><span class="token function">sort</span><span class="token punctuation">(</span>arr<span class="token punctuation">)</span><span class="token punctuation">;</span>            <span class="token comment" spellcheck="true">// 重新转换回来</span>            String str <span class="token operator">=</span> String<span class="token punctuation">.</span><span class="token function">valueOf</span><span class="token punctuation">(</span>arr<span class="token punctuation">)</span><span class="token punctuation">;</span>            <span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span>map<span class="token punctuation">.</span><span class="token function">containsKey</span><span class="token punctuation">(</span>str<span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>                <span class="token comment" spellcheck="true">// 若不存在建立映射关系，排序后的字符串成为新的List集合</span>                map<span class="token punctuation">.</span><span class="token function">put</span><span class="token punctuation">(</span>str<span class="token punctuation">,</span> <span class="token keyword">new</span> <span class="token class-name">ArrayList</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>            <span class="token punctuation">}</span>            <span class="token comment" spellcheck="true">// 建立映射关系后添加</span>            map<span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span>str<span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">add</span><span class="token punctuation">(</span>i<span class="token punctuation">)</span><span class="token punctuation">;</span>        <span class="token punctuation">}</span>        <span class="token comment" spellcheck="true">//返回值是List集合 通过构造器 构造一个包含指定 collection 的元素的列表</span>        <span class="token keyword">return</span> <span class="token keyword">new</span> <span class="token class-name">ArrayList</span><span class="token punctuation">(</span>map<span class="token punctuation">.</span><span class="token function">values</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h3 id="python代码-1"><a href="#python代码-1" class="headerlink" title="python代码"></a>python代码</h3><pre class=" language-python"><code class="language-python"><span class="token keyword">class</span> <span class="token class-name">Solution</span><span class="token punctuation">:</span>    <span class="token keyword">def</span> <span class="token function">groupAnagrams</span><span class="token punctuation">(</span>self<span class="token punctuation">,</span> strs<span class="token punctuation">:</span> List<span class="token punctuation">[</span>str<span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token operator">-</span><span class="token operator">></span> List<span class="token punctuation">[</span>List<span class="token punctuation">[</span>str<span class="token punctuation">]</span><span class="token punctuation">]</span><span class="token punctuation">:</span>        <span class="token keyword">from</span> collections <span class="token keyword">import</span> defaultdict        look <span class="token operator">=</span> defaultdict<span class="token punctuation">(</span>list<span class="token punctuation">)</span>        <span class="token keyword">for</span> s <span class="token keyword">in</span> strs<span class="token punctuation">:</span>            look<span class="token punctuation">[</span><span class="token string">""</span><span class="token punctuation">.</span>join<span class="token punctuation">(</span>sorted<span class="token punctuation">(</span>s<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">]</span><span class="token punctuation">.</span>append<span class="token punctuation">(</span>s<span class="token punctuation">)</span>        <span class="token keyword">return</span> list<span class="token punctuation">(</span>look<span class="token punctuation">.</span>values<span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span></code></pre><h2 id="三：金字塔转换矩阵"><a href="#三：金字塔转换矩阵" class="headerlink" title="三：金字塔转换矩阵"></a>三：金字塔转换矩阵</h2><h3 id="题目描述-2"><a href="#题目描述-2" class="headerlink" title="题目描述"></a>题目描述</h3><blockquote><p>现在，我们用一些方块来堆砌一个金字塔。 每个方块用仅包含一个字母的字符串表示。</p><p>使用三元组表示金字塔的堆砌规则如下：</p><p>对于三元组(A, B, C) ，“C”为顶层方块，方块“A”、“B”分别作为方块“C”下一层的的左、右子块。当且仅当(A, B, C)是被允许的三元组，我们才可以将其堆砌上。</p><p>初始时，给定金字塔的基层 bottom，用一个字符串表示。一个允许的三元组列表 allowed，每个三元组用一个长度为 3 的字符串表示。</p><p>如果可以由基层一直堆到塔尖就返回 true ，否则返回 false 。</p><p>示例 1：</p><p>输入：bottom = “BCD”, allowed = [“BCG”, “CDE”, “GEA”, “FFF”]<br>输出：true<br>解析：<br>可以堆砌成这样的金字塔:<br>    A<br>   / <br>  G   E<br> / \ / <br>B   C   D</p><p>因为符合(‘B’, ‘C’, ‘G’), (‘C’, ‘D’, ‘E’) 和 (‘G’, ‘E’, ‘A’) 三种规则。<br>示例 2：</p><p>输入：bottom = “AABA”, allowed = [“AAA”, “AAB”, “ABA”, “ABB”, “BAC”]<br>输出：false<br>解析：<br>无法一直堆到塔尖。<br>注意, 允许存在像 (A, B, C) 和 (A, B, D) 这样的三元组，其中 C != D。</p><p>提示：</p><p>bottom 的长度范围在 [2, 8]。<br>allowed 的长度范围在[0, 200]。<br>方块的标记字母范围为{‘A’, ‘B’, ‘C’, ‘D’, ‘E’, ‘F’, ‘G’}。</p></blockquote><h3 id="python代码-2"><a href="#python代码-2" class="headerlink" title="python代码"></a>python代码</h3><pre class=" language-python"><code class="language-python"><span class="token keyword">class</span> <span class="token class-name">Solution</span><span class="token punctuation">:</span>    <span class="token keyword">def</span> <span class="token function">pyramidTransition</span><span class="token punctuation">(</span>self<span class="token punctuation">,</span> bottom<span class="token punctuation">:</span> str<span class="token punctuation">,</span> allowed<span class="token punctuation">:</span> List<span class="token punctuation">[</span>str<span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token operator">-</span><span class="token operator">></span> bool<span class="token punctuation">:</span>        table <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token punctuation">}</span>        <span class="token keyword">for</span> a<span class="token punctuation">,</span> b<span class="token punctuation">,</span> c <span class="token keyword">in</span> allowed<span class="token punctuation">:</span>            table<span class="token punctuation">.</span>setdefault<span class="token punctuation">(</span>a<span class="token punctuation">,</span> <span class="token punctuation">{</span><span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">.</span>setdefault<span class="token punctuation">(</span>b<span class="token punctuation">,</span> set<span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">.</span>add<span class="token punctuation">(</span>c<span class="token punctuation">)</span>        <span class="token keyword">def</span> <span class="token function">get_next_bottoms</span><span class="token punctuation">(</span>bottom<span class="token punctuation">,</span> start<span class="token operator">=</span><span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">:</span>            <span class="token keyword">if</span> start <span class="token operator">>=</span> len<span class="token punctuation">(</span>bottom<span class="token punctuation">)</span> <span class="token operator">-</span> <span class="token number">1</span><span class="token punctuation">:</span>                <span class="token keyword">yield</span> <span class="token string">''</span>                <span class="token keyword">return</span>            a<span class="token punctuation">,</span> b <span class="token operator">=</span> bottom<span class="token punctuation">[</span>start<span class="token punctuation">]</span><span class="token punctuation">,</span> bottom<span class="token punctuation">[</span>start<span class="token operator">+</span><span class="token number">1</span><span class="token punctuation">]</span>            <span class="token keyword">if</span> a <span class="token keyword">in</span> table <span class="token operator">and</span> b <span class="token keyword">in</span> table<span class="token punctuation">[</span>a<span class="token punctuation">]</span><span class="token punctuation">:</span>                <span class="token keyword">for</span> c <span class="token keyword">in</span> table<span class="token punctuation">[</span>a<span class="token punctuation">]</span><span class="token punctuation">[</span>b<span class="token punctuation">]</span><span class="token punctuation">:</span>                    <span class="token keyword">for</span> res <span class="token keyword">in</span> get_next_bottoms<span class="token punctuation">(</span>bottom<span class="token punctuation">,</span> start<span class="token operator">+</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">:</span>                        <span class="token keyword">yield</span> c <span class="token operator">+</span> res        <span class="token keyword">def</span> <span class="token function">check</span><span class="token punctuation">(</span>bottom<span class="token punctuation">)</span><span class="token punctuation">:</span>            <span class="token keyword">return</span> len<span class="token punctuation">(</span>bottom<span class="token punctuation">)</span> <span class="token operator">==</span> <span class="token number">1</span> <span class="token operator">or</span> any<span class="token punctuation">(</span>check<span class="token punctuation">(</span>next_bottom<span class="token punctuation">)</span> <span class="token keyword">for</span> next_bottom <span class="token keyword">in</span> get_next_bottoms<span class="token punctuation">(</span>bottom<span class="token punctuation">)</span><span class="token punctuation">)</span>        <span class="token keyword">return</span> check<span class="token punctuation">(</span>bottom<span class="token punctuation">)</span></code></pre><h2 id="四：被围绕的区域"><a href="#四：被围绕的区域" class="headerlink" title="四：被围绕的区域"></a>四：被围绕的区域</h2><h3 id="题目描述-3"><a href="#题目描述-3" class="headerlink" title="题目描述"></a>题目描述</h3><blockquote><p>给定一个二维的矩阵，包含 ‘X’ 和 ‘O’（字母 O）。</p><p>找到所有被 ‘X’ 围绕的区域，并将这些区域里所有的 ‘O’ 用 ‘X’ 填充。</p><p>示例:</p><p>X X X X<br>X O O X<br>X X O X<br>X O X X<br>运行你的函数后，矩阵变为：</p><p>X X X X<br>X X X X<br>X X X X<br>X O X X<br>解释:</p><p>被围绕的区间不会存在于边界上，换句话说，任何边界上的 ‘O’ 都不会被填充为 ‘X’。 任何不在边界上，或不与边界上的 ‘O’ 相连的 ‘O’ 最终都会被填充为 ‘X’。如果两个元素在水平或垂直方向相邻，则称它们是“相连”的。</p></blockquote><h3 id="解题思路-1"><a href="#解题思路-1" class="headerlink" title="解题思路"></a>解题思路</h3><blockquote><p>典型的bfs问题，找到所有与边界‘O’相连的‘O’，标记为1，将其余标记为0的‘O’变换为‘X’</p></blockquote><h3 id="Java代码-2"><a href="#Java代码-2" class="headerlink" title="Java代码"></a>Java代码</h3><pre class=" language-java"><code class="language-java"><span class="token keyword">class</span> <span class="token class-name">Solution</span> <span class="token punctuation">{</span>    <span class="token keyword">int</span> m<span class="token punctuation">,</span> n<span class="token punctuation">;</span>    <span class="token keyword">boolean</span><span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token punctuation">]</span> visited<span class="token punctuation">;</span>    <span class="token keyword">private</span> <span class="token keyword">int</span> d<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token punctuation">{</span><span class="token operator">-</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">}</span><span class="token punctuation">,</span> <span class="token punctuation">{</span><span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">}</span><span class="token punctuation">,</span> <span class="token punctuation">{</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">}</span><span class="token punctuation">,</span> <span class="token punctuation">{</span><span class="token number">0</span><span class="token punctuation">,</span> <span class="token operator">-</span><span class="token number">1</span><span class="token punctuation">}</span><span class="token punctuation">}</span><span class="token punctuation">;</span>    <span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">solve</span><span class="token punctuation">(</span><span class="token keyword">char</span><span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token punctuation">]</span> board<span class="token punctuation">)</span> <span class="token punctuation">{</span>        <span class="token keyword">if</span><span class="token punctuation">(</span>board<span class="token punctuation">.</span>length <span class="token operator">==</span> <span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">{</span>            <span class="token keyword">return</span><span class="token punctuation">;</span>        <span class="token punctuation">}</span>        m <span class="token operator">=</span> board<span class="token punctuation">.</span>length<span class="token punctuation">;</span>        n <span class="token operator">=</span> board<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">.</span>length<span class="token punctuation">;</span>        visited <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">boolean</span><span class="token punctuation">[</span>m<span class="token punctuation">]</span><span class="token punctuation">[</span>n<span class="token punctuation">]</span><span class="token punctuation">;</span>        <span class="token comment" spellcheck="true">//首先找到所有跟外界相连的O</span>        <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i <span class="token operator">&lt;</span> m<span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>            <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> j <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> j <span class="token operator">&lt;</span> n<span class="token punctuation">;</span> j<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>                <span class="token keyword">boolean</span> isEdge <span class="token operator">=</span> i <span class="token operator">==</span> <span class="token number">0</span> <span class="token operator">||</span> j <span class="token operator">==</span> <span class="token number">0</span> <span class="token operator">||</span> i <span class="token operator">==</span> m <span class="token operator">-</span> <span class="token number">1</span> <span class="token operator">||</span> j <span class="token operator">==</span> n <span class="token operator">-</span> <span class="token number">1</span><span class="token punctuation">;</span>                <span class="token keyword">if</span> <span class="token punctuation">(</span>isEdge <span class="token operator">&amp;&amp;</span> board<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">[</span>j<span class="token punctuation">]</span> <span class="token operator">==</span> <span class="token string">'O'</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>                    <span class="token function">dfs</span><span class="token punctuation">(</span>board<span class="token punctuation">,</span> i<span class="token punctuation">,</span> j<span class="token punctuation">)</span><span class="token punctuation">;</span>                <span class="token punctuation">}</span>            <span class="token punctuation">}</span>        <span class="token punctuation">}</span>        <span class="token comment" spellcheck="true">//根据数组visited的情况进行替换</span>        <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i <span class="token operator">&lt;</span> m<span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>            <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> j <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> j <span class="token operator">&lt;</span> n<span class="token punctuation">;</span> j<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>                <span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span>visited<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">[</span>j<span class="token punctuation">]</span> <span class="token operator">&amp;&amp;</span> board<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">[</span>j<span class="token punctuation">]</span> <span class="token operator">==</span> <span class="token string">'O'</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>                    board<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">[</span>j<span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token string">'X'</span><span class="token punctuation">;</span>                <span class="token punctuation">}</span>            <span class="token punctuation">}</span>        <span class="token punctuation">}</span>    <span class="token punctuation">}</span>    <span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">dfs</span><span class="token punctuation">(</span><span class="token keyword">char</span><span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token punctuation">]</span> board<span class="token punctuation">,</span> <span class="token keyword">int</span> x<span class="token punctuation">,</span> <span class="token keyword">int</span> y<span class="token punctuation">)</span> <span class="token punctuation">{</span>        visited<span class="token punctuation">[</span>x<span class="token punctuation">]</span><span class="token punctuation">[</span>y<span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token boolean">true</span><span class="token punctuation">;</span>        <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i <span class="token operator">&lt;</span> <span class="token number">4</span><span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>            <span class="token keyword">int</span> newx <span class="token operator">=</span> x <span class="token operator">+</span> d<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">;</span>            <span class="token keyword">int</span> newy <span class="token operator">=</span> y <span class="token operator">+</span> d<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">;</span>            <span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token function">inArea</span><span class="token punctuation">(</span>newx<span class="token punctuation">,</span> newy<span class="token punctuation">)</span> <span class="token operator">&amp;&amp;</span> <span class="token operator">!</span>visited<span class="token punctuation">[</span>newx<span class="token punctuation">]</span><span class="token punctuation">[</span>newy<span class="token punctuation">]</span> <span class="token operator">&amp;&amp;</span> board<span class="token punctuation">[</span>newx<span class="token punctuation">]</span><span class="token punctuation">[</span>newy<span class="token punctuation">]</span> <span class="token operator">==</span> <span class="token string">'O'</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>                <span class="token function">dfs</span><span class="token punctuation">(</span>board<span class="token punctuation">,</span> newx<span class="token punctuation">,</span> newy<span class="token punctuation">)</span><span class="token punctuation">;</span>            <span class="token punctuation">}</span>        <span class="token punctuation">}</span>    <span class="token punctuation">}</span>    <span class="token keyword">private</span> <span class="token keyword">boolean</span> <span class="token function">inArea</span><span class="token punctuation">(</span><span class="token keyword">int</span> x<span class="token punctuation">,</span> <span class="token keyword">int</span> y<span class="token punctuation">)</span> <span class="token punctuation">{</span>        <span class="token keyword">return</span> x <span class="token operator">>=</span> <span class="token number">0</span> <span class="token operator">&amp;&amp;</span> x <span class="token operator">&lt;</span> m <span class="token operator">&amp;&amp;</span> y <span class="token operator">>=</span> <span class="token number">0</span> <span class="token operator">&amp;&amp;</span> y <span class="token operator">&lt;</span> n<span class="token punctuation">;</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h2 id="五：最小路径和"><a href="#五：最小路径和" class="headerlink" title="五：最小路径和"></a>五：最小路径和</h2><h3 id="题目描述-4"><a href="#题目描述-4" class="headerlink" title="题目描述"></a>题目描述</h3><blockquote><p>给定一个包含非负整数的 m x n 网格，请找出一条从左上角到右下角的路径，使得路径上的数字总和为最小。</p><p>说明：每次只能向下或者向右移动一步。</p><p>示例:</p><p>输入:<br>[<br>[1,3,1],<br>[1,5,1],<br>[4,2,1]<br>]<br>输出: 7<br>解释: 因为路径 1→3→1→1→1 的总和最小。</p></blockquote><h3 id="解题思路-2"><a href="#解题思路-2" class="headerlink" title="解题思路"></a>解题思路</h3><blockquote><p>这个是典型的数据结构中的最小路径问题，解题方法可用dfs+动态规划。</p></blockquote><h3 id="Java代码-3"><a href="#Java代码-3" class="headerlink" title="Java代码"></a>Java代码</h3><pre class=" language-java"><code class="language-java"><span class="token keyword">class</span> <span class="token class-name">Solution</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">int</span> <span class="token function">minPathSum</span><span class="token punctuation">(</span><span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token punctuation">]</span> grid<span class="token punctuation">)</span> <span class="token punctuation">{</span>        <span class="token keyword">if</span> <span class="token punctuation">(</span>grid <span class="token operator">==</span> null <span class="token operator">||</span> grid<span class="token punctuation">.</span>length <span class="token operator">&lt;</span> <span class="token number">1</span> <span class="token operator">||</span> grid<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span> <span class="token operator">==</span> null <span class="token operator">||</span> grid<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">.</span>length <span class="token operator">&lt;</span> <span class="token number">1</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>            <span class="token keyword">return</span> <span class="token number">0</span><span class="token punctuation">;</span>        <span class="token punctuation">}</span>             <span class="token keyword">int</span> row <span class="token operator">=</span> grid<span class="token punctuation">.</span>length<span class="token punctuation">;</span>        <span class="token keyword">int</span> col <span class="token operator">=</span> grid<span class="token punctuation">[</span>row <span class="token operator">-</span> <span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">.</span>length<span class="token punctuation">;</span>        <span class="token keyword">int</span> dp<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">int</span><span class="token punctuation">[</span>row<span class="token punctuation">]</span><span class="token punctuation">[</span>col<span class="token punctuation">]</span><span class="token punctuation">;</span>        dp<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span> <span class="token operator">=</span> grid<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">;</span>        <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> i <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">;</span>i <span class="token operator">&lt;</span> row<span class="token punctuation">;</span>i<span class="token operator">++</span><span class="token punctuation">)</span>            dp<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span> <span class="token operator">=</span> dp<span class="token punctuation">[</span>i <span class="token operator">-</span> <span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span> <span class="token operator">+</span> grid<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">;</span>                <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> i <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">;</span>i <span class="token operator">&lt;</span> col<span class="token punctuation">;</span>i<span class="token operator">++</span><span class="token punctuation">)</span>             dp<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">[</span>i<span class="token punctuation">]</span> <span class="token operator">=</span> dp<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">[</span>i <span class="token operator">-</span> <span class="token number">1</span><span class="token punctuation">]</span> <span class="token operator">+</span> grid<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">;</span>               <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> i <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">;</span>i <span class="token operator">&lt;</span> row<span class="token punctuation">;</span>i<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>            <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> j <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">;</span>j <span class="token operator">&lt;</span> col<span class="token punctuation">;</span>j<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>                dp<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">[</span>j<span class="token punctuation">]</span> <span class="token operator">=</span> Math<span class="token punctuation">.</span><span class="token function">min</span><span class="token punctuation">(</span>dp<span class="token punctuation">[</span>i <span class="token operator">-</span> <span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">[</span>j<span class="token punctuation">]</span><span class="token punctuation">,</span> dp<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">[</span>j <span class="token operator">-</span> <span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token operator">+</span> grid<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">[</span>j<span class="token punctuation">]</span><span class="token punctuation">;</span>            <span class="token punctuation">}</span>        <span class="token punctuation">}</span>        <span class="token keyword">return</span> dp<span class="token punctuation">[</span>row <span class="token operator">-</span> <span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">[</span>col <span class="token operator">-</span> <span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">;</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h3 id="python代码-3"><a href="#python代码-3" class="headerlink" title="python代码"></a>python代码</h3><pre class=" language-python"><code class="language-python"><span class="token comment" spellcheck="true"># 网上看到的大神代码，在原数组上进行最小计算，最终得到的结果</span><span class="token keyword">class</span> <span class="token class-name">Solution</span><span class="token punctuation">:</span>    <span class="token keyword">def</span> <span class="token function">minPathSum</span><span class="token punctuation">(</span>self<span class="token punctuation">,</span> grid<span class="token punctuation">:</span> List<span class="token punctuation">[</span>List<span class="token punctuation">[</span>int<span class="token punctuation">]</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token operator">-</span><span class="token operator">></span> int<span class="token punctuation">:</span>        h<span class="token punctuation">,</span> w<span class="token operator">=</span>len<span class="token punctuation">(</span>grid<span class="token punctuation">)</span><span class="token punctuation">,</span> len<span class="token punctuation">(</span>grid<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">)</span>        <span class="token keyword">for</span> j <span class="token keyword">in</span> range<span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span>w<span class="token punctuation">)</span><span class="token punctuation">:</span>            grid<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">[</span>j<span class="token punctuation">]</span><span class="token operator">+=</span>grid<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">[</span>j<span class="token number">-1</span><span class="token punctuation">]</span>        <span class="token keyword">for</span> i <span class="token keyword">in</span> range<span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span>h<span class="token punctuation">)</span><span class="token punctuation">:</span>            <span class="token keyword">for</span> j <span class="token keyword">in</span> range<span class="token punctuation">(</span>w<span class="token punctuation">)</span><span class="token punctuation">:</span>                <span class="token keyword">if</span> j<span class="token operator">==</span><span class="token number">0</span><span class="token punctuation">:</span>                    grid<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">[</span>j<span class="token punctuation">]</span><span class="token operator">+=</span>grid<span class="token punctuation">[</span>i<span class="token number">-1</span><span class="token punctuation">]</span><span class="token punctuation">[</span>j<span class="token punctuation">]</span>                <span class="token keyword">else</span><span class="token punctuation">:</span>                    grid<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">[</span>j<span class="token punctuation">]</span><span class="token operator">+=</span>min<span class="token punctuation">(</span>grid<span class="token punctuation">[</span>i<span class="token number">-1</span><span class="token punctuation">]</span><span class="token punctuation">[</span>j<span class="token punctuation">]</span><span class="token punctuation">,</span>grid<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">[</span>j<span class="token number">-1</span><span class="token punctuation">]</span><span class="token punctuation">)</span>        <span class="token keyword">return</span> grid<span class="token punctuation">[</span><span class="token operator">-</span><span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token operator">-</span><span class="token number">1</span><span class="token punctuation">]</span></code></pre>]]></content>
      
      
      
        <tags>
            
            <tag> python </tag>
            
            <tag> Java </tag>
            
            <tag> 算法 </tag>
            
        </tags>
      
    </entry>
    
    
    
    <entry>
      <title>懂点十八</title>
      <link href="/2020/06/20/dong-dian-shi-ba/"/>
      <url>/2020/06/20/dong-dian-shi-ba/</url>
      
        <content type="html"><![CDATA[<p>[TOC]</p><h2 id="在大三你应该明白的道理"><a href="#在大三你应该明白的道理" class="headerlink" title="在大三你应该明白的道理"></a>在大三你应该明白的道理</h2><h3 id="成绩"><a href="#成绩" class="headerlink" title="成绩"></a>成绩</h3><ul><li>如果你是一个普通农民家里出生的孩子，没有什么过硬的背景，只能通过自己改变自己的命运。那么你只有选择上大学、上一个名校的研究生，这是当前逆袭最可行的办法。否则我们只能被压榨。</li><li>在大学，你的成绩真的非常重要，不要再说什么“60分万岁的话”，真不知道这些话是谁传出来的，考研，保研，能考多高就考多高，别给自己留下遗憾。</li><li>在大学学习到专业知识很重要，如果你有一技之长或者说名校学历。居前者可以自保，居后者可以生活的很潇洒。非双大学的学生可以考取有含金量的证书，认认真真做实习，毕竟是金子总会发光。</li><li>多多接触你的老师，老师真的会给你很多帮助，至少要在老师心里留下一点印象。</li><li>学习是一辈子的事情，无论在哪里都要学习，但是千万不要假装学习，因为结果不会陪你演戏。</li><li>所以，走出宿舍，远离被窝，远离游戏，认认真真的开启你的逆袭之路吧。</li></ul><h3 id="谦虚"><a href="#谦虚" class="headerlink" title="谦虚"></a>谦虚</h3><ul><li>自以为自己很牛逼的人通常会被别人当作傻逼看待，当然我的意思并不是让你不表现自己，相反，你一定要勇于表现自己，证明自己的实力，但是绝不能骄傲自大，因为那样真的很傻。</li><li>不要和不在一个层级的人去争论些什么，因为不在一个阶级，考虑问题的角度不一样，利益产生方式不同，争论是没有结果的，否则就会自贬身价，拉低自己的智商。</li><li>总之，不要装逼，装逼遭雷劈。你只需要默默的成长、变强，在适当的时候表现自己就够了。</li></ul><h3 id="明确"><a href="#明确" class="headerlink" title="明确"></a>明确</h3><ul><li>一定要清楚，这个世界很现实，也许有很多不公平，也许你真的怀才不遇，也许你真的受了委屈，也许……但是不可否认，我喜欢这个世界，我珍爱自己的生命，因为这个世界至少给我们机会，让我们去改变一些东西。</li><li>一定要有一个明确的大方向，否则你就是在原地转圈圈。</li><li>不要以锻炼为名做自己不擅长的事情，在大学，每个人都有自己的价值，你只需要找到自己热爱的事情，然后去像这个方向发展，去努力成为这个方向的金字塔顶就够了。</li><li>要谨慎地做出每一个决定，要明确自己的人生，给自己一个目标，你给我时间，我还你奇迹。</li><li>永远不要在假期的时候带很多书回家，你怎么带回去的就一定会怎么原封不动的带回来。因此，在放假前做的那些学习设想就永远只能是设想。</li></ul><h3 id="后悔"><a href="#后悔" class="headerlink" title="后悔"></a>后悔</h3><ul><li>我最后悔的一件事情就是没有继续前进担任学习部的副部，当时给自己找了很多理由退缩，在现在看来都是借口。</li></ul><h3 id="幸运"><a href="#幸运" class="headerlink" title="幸运"></a>幸运</h3><ul><li>的确，我在大学最幸运的事情就是成功加入了Android实验室并不断成长，在这里有必要提一下，Android实验室的选拔是非常严格的，因为经过几届的发展，Android实验室逐步壮大，有很多人想要加入，可以说选拔制度就是十进一，因此我非常幸运，在实验室里慢慢成长，认识了很多优秀的学长学姐，在实验室已经差不多两年了，虽然感觉自己依旧很菜，然是比起同级的学生，差距还是有的。</li><li>还有一个非常幸运的事情就是我加入了学习部，这真的是一个非常有爱的集体，虽然平时的工作很忙，学长们很严格，但是却能给我们带来成长。但我想说的是，在学习部，你可以感受到一种温暖，就像家的感觉，很开心，也很严格。不管出于什么样的原因我大二没有继续留在部门，但是我发自内心的喜欢这个集体。</li></ul><p><strong><u>致正在读大学的你们或者是即将要读大学的你们还有我，我马上就要升大三了，写点东西勉励自己</u></strong></p><blockquote><p><strong>大学时光已经过去一半，还有一半时间可以说真的很快，快到让你来不及反应就已经要毕业了，因此如果你有幸看到这篇文章，就要好好的想一想，早做准备……</strong></p></blockquote>]]></content>
      
      
      
        <tags>
            
            <tag> 杂记 </tag>
            
        </tags>
      
    </entry>
    
    
    
    <entry>
      <title>Java 基础知识(2)</title>
      <link href="/2020/06/19/java-ji-chu-zhi-shi-2/"/>
      <url>/2020/06/19/java-ji-chu-zhi-shi-2/</url>
      
        <content type="html"><![CDATA[<p>[TOC]</p><h1 id="面向对象基础知识-二"><a href="#面向对象基础知识-二" class="headerlink" title="面向对象基础知识(二)"></a>面向对象基础知识(二)</h1><h2 id="string基本概念"><a href="#string基本概念" class="headerlink" title="string基本概念"></a>string基本概念</h2><h3 id="为string类对象直接赋值"><a href="#为string类对象直接赋值" class="headerlink" title="为string类对象直接赋值"></a>为string类对象直接赋值</h3><pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">StringDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>        String str <span class="token operator">=</span> <span class="token string">"www.baidu.com"</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 直接赋值</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>str<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 输出字符串数据</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h3 id="利用构造方法实例化"><a href="#利用构造方法实例化" class="headerlink" title="利用构造方法实例化"></a>利用构造方法实例化</h3><pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">StringDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>        String str <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">String</span><span class="token punctuation">(</span><span class="token string">"www.baidu.com"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 直接赋值</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>str<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 输出字符串数据</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h3 id="在string对象上使用等号比较"><a href="#在string对象上使用等号比较" class="headerlink" title="在string对象上使用等号比较"></a>在string对象上使用等号比较</h3><ul><li>在string对象上使用”==”比较</li></ul><pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">StringDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>        String stra <span class="token operator">=</span> <span class="token string">"hello"</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 直接赋值定义字符串</span>        String strb <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">String</span><span class="token punctuation">(</span><span class="token string">"hello"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 构造方法定义字符串</span>        String strc <span class="token operator">=</span> strb<span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 引用传递</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>stra <span class="token operator">==</span> strb<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 比较结果：false</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>stra <span class="token operator">==</span> strc<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 比较结果：false</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>strb <span class="token operator">==</span> strc<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 比较结果：true</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h3 id="实现字符串内容比较"><a href="#实现字符串内容比较" class="headerlink" title="实现字符串内容比较"></a>实现字符串内容比较</h3><pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">StringDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>        String stra <span class="token operator">=</span> <span class="token string">"hello"</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 直接赋值定义字符串</span>        String strb <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">String</span><span class="token punctuation">(</span><span class="token string">"hello"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 构造方法定义字符串</span>        String strc <span class="token operator">=</span> strb<span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 引用传递</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>stra<span class="token punctuation">.</span><span class="token function">equals</span><span class="token punctuation">(</span>strb<span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 比较结果：true</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>stra<span class="token punctuation">.</span><span class="token function">equals</span><span class="token punctuation">(</span>strc<span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 比较结果：true</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>strb<span class="token punctuation">.</span><span class="token function">equals</span><span class="token punctuation">(</span>strc<span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 比较结果：true</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h3 id="直接赋值时的堆内存自动引用"><a href="#直接赋值时的堆内存自动引用" class="headerlink" title="直接赋值时的堆内存自动引用"></a>直接赋值时的堆内存自动引用</h3><pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">StringDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>        String stra <span class="token operator">=</span> <span class="token string">"hello"</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 直接赋值实例化</span>        String strb <span class="token operator">=</span> <span class="token string">"hello"</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 直接赋值实例化</span>        String strc <span class="token operator">=</span> <span class="token string">"hello"</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 直接赋值实例化</span>        String strd <span class="token operator">=</span> <span class="token string">"yootk"</span> <span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 直接赋值实例化，内容不相同</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>stra <span class="token operator">==</span> strb<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 判断结果：true</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>stra <span class="token operator">==</span> strc<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 判断结果：true</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>strb <span class="token operator">==</span> strc<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 判断结果：true</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>stra <span class="token operator">==</span> strd<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 判断结果：false</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h3 id="不自动保存对象池操作"><a href="#不自动保存对象池操作" class="headerlink" title="不自动保存对象池操作"></a>不自动保存对象池操作</h3><pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">StringDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>        String stra <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">String</span><span class="token punctuation">(</span><span class="token string">"hello"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 使用构造方法定义了新的内存空间，不会自动入池</span>        String strb <span class="token operator">=</span> <span class="token string">"hello"</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 直接赋值</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>stra <span class="token operator">==</span> strb<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 判断结果：false</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h3 id="手工入池"><a href="#手工入池" class="headerlink" title="手工入池"></a>手工入池</h3><pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">StringDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>        String stra <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">String</span><span class="token punctuation">(</span><span class="token string">"hello"</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">intern</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 使用构造方法定义新的内存空间，手工入池</span>        String strb <span class="token operator">=</span> <span class="token string">"hello"</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 直接赋值</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>stra <span class="token operator">==</span> strb<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 判断结果：true</span>    <span class="token punctuation">}</span>ja<span class="token punctuation">}</span></code></pre><h3 id="修改字符串对象引用"><a href="#修改字符串对象引用" class="headerlink" title="修改字符串对象引用"></a>修改字符串对象引用</h3><pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">StringDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>        String str <span class="token operator">=</span> <span class="token string">"Hello "</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 直接赋值实例化String类对象</span>        str <span class="token operator">=</span> str <span class="token operator">+</span> <span class="token string">"World "</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 字符串连接，同时修改String类对象的引用关系</span>        str <span class="token operator">+=</span> <span class="token string">"!!!"</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 字符串连接，同时修改String类对象的引用关系</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>str<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 输出当前的String类对象内容</span>        <span class="token comment" spellcheck="true">//Hello World !!!</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h2 id="string类的常用方法"><a href="#string类的常用方法" class="headerlink" title="string类的常用方法"></a>string类的常用方法</h2><h3 id="取出指定索引的字符"><a href="#取出指定索引的字符" class="headerlink" title="取出指定索引的字符"></a>取出指定索引的字符</h3><pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">StringDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>        String str <span class="token operator">=</span> <span class="token string">"hello"</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 定义字符串对象</span>        <span class="token keyword">char</span> c <span class="token operator">=</span> str<span class="token punctuation">.</span><span class="token function">charAt</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 截取第一个字符</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>c<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 输出字符</span>        <span class="token comment" spellcheck="true">// h</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h3 id="字符数组与字符串的转换"><a href="#字符数组与字符串的转换" class="headerlink" title="字符数组与字符串的转换"></a>字符数组与字符串的转换</h3><pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">StringDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>        String str <span class="token operator">=</span> <span class="token string">"hello"</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 定义字符串</span>        <span class="token keyword">char</span><span class="token punctuation">[</span><span class="token punctuation">]</span> data <span class="token operator">=</span> str<span class="token punctuation">.</span><span class="token function">toCharArray</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 将字符串变为字符数组</span>        <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> x <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> x <span class="token operator">&lt;</span> data<span class="token punctuation">.</span>length<span class="token punctuation">;</span> x<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token comment" spellcheck="true">// 循环输出每一个字符</span>            System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">print</span><span class="token punctuation">(</span>data<span class="token punctuation">[</span>x<span class="token punctuation">]</span> <span class="token operator">+</span> <span class="token string">"、"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>        <span class="token punctuation">}</span>        <span class="token comment" spellcheck="true">// h、e、l、l、o、</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h3 id="将字符串转为大写"><a href="#将字符串转为大写" class="headerlink" title="将字符串转为大写"></a>将字符串转为大写</h3><pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">StringDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>        String str <span class="token operator">=</span> <span class="token string">"hello"</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 字符串由小写字母组成</span>        <span class="token keyword">char</span><span class="token punctuation">[</span><span class="token punctuation">]</span> data <span class="token operator">=</span> str<span class="token punctuation">.</span><span class="token function">toCharArray</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 将字符串变为字符数组</span>        <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> x <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> x <span class="token operator">&lt;</span> data<span class="token punctuation">.</span>length<span class="token punctuation">;</span> x<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token comment" spellcheck="true">// 改变每一个字符的编码值</span>            data<span class="token punctuation">[</span>x<span class="token punctuation">]</span> <span class="token operator">-=</span> <span class="token number">32</span><span class="token punctuation">;</span>        <span class="token punctuation">}</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token keyword">new</span> <span class="token class-name">String</span><span class="token punctuation">(</span>data<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 将全部字符数组变为String</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token keyword">new</span> <span class="token class-name">String</span><span class="token punctuation">(</span>data<span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 将部分字符数组变为String</span>        <span class="token comment" spellcheck="true">// HELLO</span>        <span class="token comment" spellcheck="true">// EL</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h3 id="判断字符串是否由数字组成"><a href="#判断字符串是否由数字组成" class="headerlink" title="判断字符串是否由数字组成"></a>判断字符串是否由数字组成</h3><pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">StringDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>        String str <span class="token operator">=</span> <span class="token string">"123423432"</span><span class="token punctuation">;</span>        <span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token function">isNumber</span><span class="token punctuation">(</span>str<span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>          System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"字符串由数字组成！"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>        <span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token punctuation">{</span>          System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"字符串由非数字组成！"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>        <span class="token punctuation">}</span>    <span class="token punctuation">}</span>    <span class="token comment" spellcheck="true">/**     * 判断字符串是否由数字所组成     * @param temp 要判断的字符串数据     * @return 如果字符串由数字组成返回true，否则返回false     */</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">boolean</span> <span class="token function">isNumber</span><span class="token punctuation">(</span>String temp<span class="token punctuation">)</span> <span class="token punctuation">{</span>        <span class="token keyword">char</span><span class="token punctuation">[</span><span class="token punctuation">]</span> data <span class="token operator">=</span> temp<span class="token punctuation">.</span><span class="token function">toCharArray</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 将字符串变为字符数组，可以取出每一位字符进行判断</span>        <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> x <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> x <span class="token operator">&lt;</span> data<span class="token punctuation">.</span>length<span class="token punctuation">;</span> x<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token comment" spellcheck="true">// 循环判断</span>            <span class="token keyword">if</span> <span class="token punctuation">(</span>data<span class="token punctuation">[</span>x<span class="token punctuation">]</span> <span class="token operator">></span> <span class="token string">'9'</span> <span class="token operator">||</span> data<span class="token punctuation">[</span>x<span class="token punctuation">]</span> <span class="token operator">&lt;</span> <span class="token string">'0'</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token comment" spellcheck="true">// 不是数字字符范围</span>              <span class="token keyword">return</span> <span class="token boolean">false</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 后续不再判断</span>            <span class="token punctuation">}</span>        <span class="token punctuation">}</span>        <span class="token keyword">return</span> <span class="token boolean">true</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 如果全部验证通过返回true</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h3 id="字符串与字节数组的转换"><a href="#字符串与字节数组的转换" class="headerlink" title="字符串与字节数组的转换"></a>字符串与字节数组的转换</h3><pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">StringDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>        String str <span class="token operator">=</span> <span class="token string">"helloworld"</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 定义字符串</span>        <span class="token keyword">byte</span><span class="token punctuation">[</span><span class="token punctuation">]</span> data <span class="token operator">=</span> str<span class="token punctuation">.</span><span class="token function">getBytes</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 将字符串变为字节数组</span>        <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> x <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> x <span class="token operator">&lt;</span> data<span class="token punctuation">.</span>length<span class="token punctuation">;</span> x<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>            data<span class="token punctuation">[</span>x<span class="token punctuation">]</span> <span class="token operator">-=</span> <span class="token number">32</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 将小写字母变为大写形式</span>        <span class="token punctuation">}</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token keyword">new</span> <span class="token class-name">String</span><span class="token punctuation">(</span>data<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 全部转换</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token keyword">new</span> <span class="token class-name">String</span><span class="token punctuation">(</span>data<span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 部分转换</span>        <span class="token comment" spellcheck="true">/*        HELLOWORLD        WORLD        */</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h3 id="字符串比较的方法"><a href="#字符串比较的方法" class="headerlink" title="字符串比较的方法"></a>字符串比较的方法</h3><ul><li>compareTo()方法</li></ul><pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">StringDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>        String stra <span class="token operator">=</span> <span class="token string">"Hello"</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 定义字符串对象</span>        String strb <span class="token operator">=</span> <span class="token string">"HEllo"</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 定义字符串对象</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>stra<span class="token punctuation">.</span><span class="token function">compareTo</span><span class="token punctuation">(</span>strb<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 32，大于0</span>        <span class="token keyword">if</span> <span class="token punctuation">(</span>stra<span class="token punctuation">.</span><span class="token function">compareTo</span><span class="token punctuation">(</span>strb<span class="token punctuation">)</span> <span class="token operator">></span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token comment" spellcheck="true">// 可以利用大小等于0的方式来判断大小</span>           System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"大于"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>        <span class="token punctuation">}</span>        <span class="token comment" spellcheck="true">/*        32        大于        */</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h3 id="字符串查找的方法"><a href="#字符串查找的方法" class="headerlink" title="字符串查找的方法"></a>字符串查找的方法</h3><ul><li>使用indexOf()等功能查找</li></ul><pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">StringDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>        String str <span class="token operator">=</span> <span class="token string">"helloworld"</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 实例化字符串对象</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>str<span class="token punctuation">.</span><span class="token function">indexOf</span><span class="token punctuation">(</span><span class="token string">"world"</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 返回满足条件单词的第一个字母的索引</span>        <span class="token comment" spellcheck="true">// 5</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>str<span class="token punctuation">.</span><span class="token function">indexOf</span><span class="token punctuation">(</span><span class="token string">"l"</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 返回的是第一个查找到的子字符串位置</span>        <span class="token comment" spellcheck="true">// 2 </span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>str<span class="token punctuation">.</span><span class="token function">indexOf</span><span class="token punctuation">(</span><span class="token string">"l"</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 从第6个元素开始查找子字符串位置</span>        <span class="token comment" spellcheck="true">// 8</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>str<span class="token punctuation">.</span><span class="token function">lastIndexOf</span><span class="token punctuation">(</span><span class="token string">"l"</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 从后向前开始查找指定字符串的位置</span>        <span class="token comment" spellcheck="true">// 8</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h3 id="判断子字符串是否存在的第一种string方法"><a href="#判断子字符串是否存在的第一种string方法" class="headerlink" title="判断子字符串是否存在的第一种string方法"></a>判断子字符串是否存在的第一种string方法</h3><ul><li>利用indexOf()方法判断子字符串是否存在</li></ul><pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">StringDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>        String str <span class="token operator">=</span> <span class="token string">"helloworld"</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 字符串对象</span>        <span class="token keyword">if</span> <span class="token punctuation">(</span>str<span class="token punctuation">.</span><span class="token function">indexOf</span><span class="token punctuation">(</span><span class="token string">"world"</span><span class="token punctuation">)</span> <span class="token operator">!=</span> <span class="token operator">-</span><span class="token number">1</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token comment" spellcheck="true">// 能找到子字符串</span>          System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"可以查询到数据"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>        <span class="token punctuation">}</span>        <span class="token comment" spellcheck="true">// 可以查询到数据</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h3 id="判断子字符串是否存在的第二种string方法"><a href="#判断子字符串是否存在的第二种string方法" class="headerlink" title="判断子字符串是否存在的第二种string方法"></a>判断子字符串是否存在的第二种string方法</h3><ul><li>使用contains()方法判断子字符串是否存在</li></ul><pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">StringDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>        String str <span class="token operator">=</span> <span class="token string">"helloworld"</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 字符串对象</span>        <span class="token keyword">if</span> <span class="token punctuation">(</span>str<span class="token punctuation">.</span><span class="token function">contains</span><span class="token punctuation">(</span><span class="token string">"world"</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token comment" spellcheck="true">// 子字符串存在</span>            System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"可以查询到数据。"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>        <span class="token punctuation">}</span>        <span class="token comment" spellcheck="true">// 可以查询到数据</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h3 id="开头或结尾判断"><a href="#开头或结尾判断" class="headerlink" title="开头或结尾判断"></a>开头或结尾判断</h3><pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">StringDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>        String str <span class="token operator">=</span> <span class="token string">"##@@hello**"</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 字符串对象</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>str<span class="token punctuation">.</span><span class="token function">startsWith</span><span class="token punctuation">(</span><span class="token string">"##"</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 是否以“##”开头</span>        <span class="token comment" spellcheck="true">/// ture</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>str<span class="token punctuation">.</span><span class="token function">startsWith</span><span class="token punctuation">(</span><span class="token string">"@@"</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 从第2个索引开始是否以“@@”开头</span>        <span class="token comment" spellcheck="true">// ture</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>str<span class="token punctuation">.</span><span class="token function">startsWith</span><span class="token punctuation">(</span><span class="token string">"**"</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 是否以“**”结尾</span>        <span class="token comment" spellcheck="true">// false</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h3 id="观察替换的结果"><a href="#观察替换的结果" class="headerlink" title="观察替换的结果"></a>观察替换的结果</h3><pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">StringDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>        String str <span class="token operator">=</span> <span class="token string">"helloworld"</span> <span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 定义字符串</span>        String resultA <span class="token operator">=</span> str<span class="token punctuation">.</span><span class="token function">replaceAll</span><span class="token punctuation">(</span><span class="token string">"l"</span><span class="token punctuation">,</span><span class="token string">"_"</span><span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 全部替换</span>        String resultB <span class="token operator">=</span> str<span class="token punctuation">.</span><span class="token function">replaceFirst</span><span class="token punctuation">(</span><span class="token string">"l"</span><span class="token punctuation">,</span><span class="token string">"_"</span><span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 替换首个</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>resultA<span class="token punctuation">)</span> <span class="token punctuation">;</span>        <span class="token comment" spellcheck="true">// he__owor_d</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>resultB<span class="token punctuation">)</span> <span class="token punctuation">;</span>        <span class="token comment" spellcheck="true">// he_loworld</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h3 id="截取数据"><a href="#截取数据" class="headerlink" title="截取数据"></a>截取数据</h3><pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">StringDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>        String str <span class="token operator">=</span> <span class="token string">"helloworld"</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 定义字符串</span>        String resultA <span class="token operator">=</span> str<span class="token punctuation">.</span><span class="token function">substring</span><span class="token punctuation">(</span><span class="token number">5</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 从指定索引截取到结尾</span>        String resultB <span class="token operator">=</span> str<span class="token punctuation">.</span><span class="token function">substring</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 截取部分子字符串</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>resultA<span class="token punctuation">)</span><span class="token punctuation">;</span>        <span class="token comment" spellcheck="true">// world</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>resultB<span class="token punctuation">)</span><span class="token punctuation">;</span>        <span class="token comment" spellcheck="true">// hello</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h3 id="字符串拆分单词"><a href="#字符串拆分单词" class="headerlink" title="字符串拆分单词"></a>字符串拆分单词</h3><pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">StringDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>        String str <span class="token operator">=</span> <span class="token string">"hello i like you"</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 定义字符串，中间使用空格作为间隔</span>        String result<span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token operator">=</span> str<span class="token punctuation">.</span><span class="token function">split</span><span class="token punctuation">(</span><span class="token string">" "</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 字符串拆分</span>        <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> x <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> x <span class="token operator">&lt;</span> result<span class="token punctuation">.</span>length<span class="token punctuation">;</span> x<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token comment" spellcheck="true">// 循环输出</span>            System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">print</span><span class="token punctuation">(</span>result<span class="token punctuation">[</span>x<span class="token punctuation">]</span> <span class="token operator">+</span> <span class="token string">"、"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>        <span class="token punctuation">}</span>        <span class="token comment" spellcheck="true">// hello、i、like、you、</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h3 id="字符串拆分字母"><a href="#字符串拆分字母" class="headerlink" title="字符串拆分字母"></a>字符串拆分字母</h3><pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">StringDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>        String str <span class="token operator">=</span> <span class="token string">"hello i like you"</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 定义字符串</span>        String result<span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token operator">=</span> str<span class="token punctuation">.</span><span class="token function">split</span><span class="token punctuation">(</span><span class="token string">""</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 字符串全部拆分</span>        <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> x <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> x <span class="token operator">&lt;</span> result<span class="token punctuation">.</span>length<span class="token punctuation">;</span> x<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token comment" spellcheck="true">// 循环输出</span>            System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">print</span><span class="token punctuation">(</span>result<span class="token punctuation">[</span>x<span class="token punctuation">]</span> <span class="token operator">+</span> <span class="token string">"、"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>        <span class="token punctuation">}</span>        <span class="token comment" spellcheck="true">// h、e、l、l、o、 、i、 、l、i、k、e、 、y、o、u、</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h3 id="拆分为指定的个数"><a href="#拆分为指定的个数" class="headerlink" title="拆分为指定的个数"></a>拆分为指定的个数</h3><pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">StringDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>         String str <span class="token operator">=</span> <span class="token string">"hello i like you"</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 定义字符串，中间使用空格作为间隔</span>        String result<span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token operator">=</span> str<span class="token punctuation">.</span><span class="token function">split</span><span class="token punctuation">(</span><span class="token string">" "</span><span class="token punctuation">,</span><span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 字符串拆分</span>        <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> x <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> x <span class="token operator">&lt;</span> result<span class="token punctuation">.</span>length<span class="token punctuation">;</span> x<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token comment" spellcheck="true">// 循环输出</span>            System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>result<span class="token punctuation">[</span>x<span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span>        <span class="token punctuation">}</span>        <span class="token comment" spellcheck="true">/*        hello        i like you        */</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h3 id="拆分例子"><a href="#拆分例子" class="headerlink" title="拆分例子"></a>拆分例子</h3><pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">StringDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>        String str <span class="token operator">=</span> <span class="token string">"张三:20|李四:21|王五:22"</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 定义字符串</span>        String result<span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token operator">=</span> str<span class="token punctuation">.</span><span class="token function">split</span><span class="token punctuation">(</span><span class="token string">"\\|"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 第一次拆分</span>        <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> x <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> x <span class="token operator">&lt;</span> result<span class="token punctuation">.</span>length<span class="token punctuation">;</span> x<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>           String temp<span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token operator">=</span> result<span class="token punctuation">[</span>x<span class="token punctuation">]</span><span class="token punctuation">.</span><span class="token function">split</span><span class="token punctuation">(</span><span class="token string">":"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 第二次拆分</span>           System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"姓名："</span> <span class="token operator">+</span> temp<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span> <span class="token operator">+</span> <span class="token string">"，年龄："</span> <span class="token operator">+</span> temp<span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span>        <span class="token punctuation">}</span>        <span class="token comment" spellcheck="true">/*            姓名：张三，年龄：20            姓名：李四，年龄：21            姓名：王五，年龄：22        */</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h3 id="字符串连接"><a href="#字符串连接" class="headerlink" title="字符串连接"></a>字符串连接</h3><pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">StringDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>        String str <span class="token operator">=</span> <span class="token string">"hello"</span><span class="token punctuation">.</span><span class="token function">concat</span><span class="token punctuation">(</span><span class="token string">"world"</span><span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 等价于“+”</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>str<span class="token punctuation">)</span> <span class="token punctuation">;</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span><span class="token comment" spellcheck="true">/*hello world*/</span></code></pre><h3 id="转小写与转大写操作"><a href="#转小写与转大写操作" class="headerlink" title="转小写与转大写操作"></a>转小写与转大写操作</h3><pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">StringDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>        String str <span class="token operator">=</span> <span class="token string">"(*(*Hello(*(*"</span> <span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 定义字符串</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>str<span class="token punctuation">.</span><span class="token function">toUpperCase</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 转大写后输出</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>str<span class="token punctuation">.</span><span class="token function">toLowerCase</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 转小写后输出</span>        <span class="token comment" spellcheck="true">/*            (*(*HELLO(*(*            (*(*hello(*(*        */</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h3 id="去掉左右空格"><a href="#去掉左右空格" class="headerlink" title="去掉左右空格"></a>去掉左右空格</h3><pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">StringDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>        String str <span class="token operator">=</span> <span class="token string">"   hello   world  "</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 定义字符串，包含空格</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"【"</span> <span class="token operator">+</span> str <span class="token operator">+</span> <span class="token string">"】"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 原始字符串</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"【"</span> <span class="token operator">+</span> str<span class="token punctuation">.</span><span class="token function">trim</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token string">"】"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 去掉空格后的字符串</span>        <span class="token comment" spellcheck="true">/*            【   hello   world  】            【hello   world】        */</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h3 id="取消掉全部空格"><a href="#取消掉全部空格" class="headerlink" title="取消掉全部空格"></a>取消掉全部空格</h3><pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">StringDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>        String str <span class="token operator">=</span> <span class="token string">"   hello   world  "</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 定义字符串，包含空格</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>str<span class="token punctuation">.</span><span class="token function">replaceAll</span><span class="token punctuation">(</span><span class="token string">" "</span><span class="token punctuation">,</span><span class="token string">""</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 去掉空格后的字符串</span>        <span class="token comment" spellcheck="true">// helloworld</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h3 id="取得字符串长度"><a href="#取得字符串长度" class="headerlink" title="取得字符串长度"></a>取得字符串长度</h3><pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">StringDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>        String str <span class="token operator">=</span> <span class="token string">"helloworld"</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 定义字符串</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>str<span class="token punctuation">.</span><span class="token function">length</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 取得字符串长度</span>        <span class="token comment" spellcheck="true">// 10</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>str<span class="token punctuation">.</span><span class="token function">isEmpty</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 判断字符串对象的内容是否为空字符串（不是null）</span>        <span class="token comment" spellcheck="true">// false</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">""</span><span class="token punctuation">.</span><span class="token function">isEmpty</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 判断字符串常量的内容是否为空字符串（不是null）</span>        <span class="token comment" spellcheck="true">// true</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h3 id="实现首字母大写的操作"><a href="#实现首字母大写的操作" class="headerlink" title="实现首字母大写的操作"></a>实现首字母大写的操作</h3><pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">StringDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>        String str <span class="token operator">=</span> <span class="token string">"wanghao"</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 定义字符串</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token function">initcap</span><span class="token punctuation">(</span>str<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 调用initcap()方法</span>        <span class="token comment" spellcheck="true">// Wanghao</span>    <span class="token punctuation">}</span>    <span class="token comment" spellcheck="true">/**     * 实现首字母大写的操作     * @param temp 要转换的字符串数据     * @return 将首字母大写后返回     */</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> String <span class="token function">initcap</span><span class="token punctuation">(</span>String temp<span class="token punctuation">)</span> <span class="token punctuation">{</span>        <span class="token comment" spellcheck="true">// 利用substring(0,1)取出字符串的第一位后将其变为大写，再连接剩余的字符串</span>        <span class="token keyword">return</span> temp<span class="token punctuation">.</span><span class="token function">substring</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">toUpperCase</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">+</span> temp<span class="token punctuation">.</span><span class="token function">substring</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre>]]></content>
      
      
      
        <tags>
            
            <tag> Java </tag>
            
        </tags>
      
    </entry>
    
    
    
    <entry>
      <title>Java 基础知识(1)</title>
      <link href="/2020/06/19/java-ji-chu-zhi-shi-1/"/>
      <url>/2020/06/19/java-ji-chu-zhi-shi-1/</url>
      
        <content type="html"><![CDATA[<p>[TOC]</p><h1 id="面向对象基础知识（一）"><a href="#面向对象基础知识（一）" class="headerlink" title="面向对象基础知识（一）"></a>面向对象基础知识（一）</h1><ul><li><blockquote><p>类与对象</p><ul><li>定义一个自己的类</li><li>使用类——在主类中使用Book类</li></ul></blockquote></li></ul><h2 id="类与对象"><a href="#类与对象" class="headerlink" title="类与对象"></a>类与对象</h2><h3 id="自定义的类"><a href="#自定义的类" class="headerlink" title="自定义的类"></a>自定义的类</h3><ul><li><strong>通过class标识符进行声明</strong></li></ul><pre class=" language-java"><code class="language-java"><span class="token keyword">class</span> <span class="token class-name">Book</span> <span class="token punctuation">{</span> <span class="token comment" spellcheck="true">// 定义一个新的类</span>    String title<span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 书的名字</span>    <span class="token keyword">double</span> price<span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 书的价格</span>    <span class="token comment" spellcheck="true">/**     * 输出对象完整信息     */</span>    <span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">getInfo</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token comment" spellcheck="true">// 此方法将由对象调用</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"图书名称："</span> <span class="token operator">+</span> title <span class="token operator">+</span> <span class="token string">"，价格："</span> <span class="token operator">+</span> price<span class="token punctuation">)</span><span class="token punctuation">;</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h3 id="在主类中使用类"><a href="#在主类中使用类" class="headerlink" title="在主类中使用类"></a>在主类中使用类</h3><ul><li><strong>在主类中使用Book类</strong></li></ul><pre class=" language-java"><code class="language-java"><span class="token keyword">class</span> <span class="token class-name">Book</span> <span class="token punctuation">{</span> <span class="token comment" spellcheck="true">// 定义一个新的类</span>    String title<span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 书的名字</span>    <span class="token keyword">double</span> price<span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 书的价格</span>    <span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">getInfo</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token comment" spellcheck="true">// 此方法将由对象调用</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"图书名称："</span> <span class="token operator">+</span> title <span class="token operator">+</span> <span class="token string">"，价格："</span> <span class="token operator">+</span> price<span class="token punctuation">)</span><span class="token punctuation">;</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">TestDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>        Book bk <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Book</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 声明并实例化对象</span>        bk<span class="token punctuation">.</span>title <span class="token operator">=</span> <span class="token string">"Java开发"</span> <span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 操作属性内容</span>        bk<span class="token punctuation">.</span>price <span class="token operator">=</span> <span class="token number">89.9</span> <span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 操作属性内容</span>        bk<span class="token punctuation">.</span><span class="token function">getInfo</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 调用类中的getInfo()方法</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h3 id="以分步式的方式实例化对象"><a href="#以分步式的方式实例化对象" class="headerlink" title="以分步式的方式实例化对象"></a>以分步式的方式实例化对象</h3><pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">TestDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>        Book bk <span class="token operator">=</span> null<span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 声明对象</span>        bk <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Book</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 实例化对象（开辟了堆内存）</span>        bk<span class="token punctuation">.</span>title <span class="token operator">=</span> <span class="token string">"Java开发"</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 操作属性内容</span>        bk<span class="token punctuation">.</span>price <span class="token operator">=</span> <span class="token number">89.9</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 操作属性内容</span>        bk<span class="token punctuation">.</span><span class="token function">getInfo</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 调用类中的getInfo()方法</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h2 id="封装性初步分析"><a href="#封装性初步分析" class="headerlink" title="封装性初步分析"></a>封装性初步分析</h2><h3 id="没有封装的代码"><a href="#没有封装的代码" class="headerlink" title="没有封装的代码"></a>没有封装的代码</h3><pre class=" language-java"><code class="language-java"><span class="token keyword">class</span> <span class="token class-name">Book</span> <span class="token punctuation">{</span> <span class="token comment" spellcheck="true">// 定义一个新的类</span>    String title<span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 书的名字</span>    <span class="token keyword">double</span> price<span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 书的价格</span>    <span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">getInfo</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token comment" spellcheck="true">// 此方法将由对象调用</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"图书名称："</span> <span class="token operator">+</span> title <span class="token operator">+</span> <span class="token string">"，价格："</span> <span class="token operator">+</span> price<span class="token punctuation">)</span><span class="token punctuation">;</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">TestDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>        Book book <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Book</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 声明并实例化对象</span>        book<span class="token punctuation">.</span>title <span class="token operator">=</span> <span class="token string">"Java开发"</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 设置属性内容</span>        book<span class="token punctuation">.</span>price <span class="token operator">=</span> <span class="token operator">-</span><span class="token number">89.9</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 设置属性内容</span>        book<span class="token punctuation">.</span><span class="token function">getInfo</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 调用方法</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h3 id="使用private封装属性"><a href="#使用private封装属性" class="headerlink" title="使用private封装属性"></a>使用private封装属性</h3><pre class=" language-java"><code class="language-java"><span class="token keyword">class</span> <span class="token class-name">Book</span> <span class="token punctuation">{</span> <span class="token comment" spellcheck="true">// 定义一个新的类</span>    <span class="token keyword">private</span> String title<span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 书的名字</span>    <span class="token keyword">private</span> <span class="token keyword">double</span> price<span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 书的价格</span>    <span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">getInfo</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token comment" spellcheck="true">// 此方法将由对象调用</span>        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"图书名称："</span> <span class="token operator">+</span> title <span class="token operator">+</span> <span class="token string">"，价格："</span> <span class="token operator">+</span> price<span class="token punctuation">)</span><span class="token punctuation">;</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">TestDemo</span> <span class="token punctuation">{</span>    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>        Book book <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Book</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 声明并实例化对象</span>        book<span class="token punctuation">.</span>title <span class="token operator">=</span> <span class="token string">"Java开发"</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 设置属性内容</span>        book<span class="token punctuation">.</span>price <span class="token operator">=</span> <span class="token operator">-</span><span class="token number">89.9</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 设置属性内容</span>        book<span class="token punctuation">.</span><span class="token function">getInfo</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 调用方法</span>    <span class="token punctuation">}</span><span class="token punctuation">}</span></code></pre><h2 id="为封装属性设置取数据操作"><a href="#为封装属性设置取数据操作" class="headerlink" title="为封装属性设置取数据操作"></a>为封装属性设置取数据操作</h2><ul><li>为Book类中的封装属性设置setter、getter操作</li></ul><pre class=" language-java"><code class="language-java"> <span class="token keyword">class</span> <span class="token class-name">Book</span> <span class="token punctuation">{</span> <span class="token comment" spellcheck="true">// 定义一个新的类</span>     <span class="token keyword">private</span> String title<span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 书的名字</span>     <span class="token keyword">private</span> <span class="token keyword">double</span> price<span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 书的价格</span>     <span class="token comment" spellcheck="true">/**      * 设置或修改title属性内容      * @param t 接收要设置的数据      */</span>     <span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">setTitle</span><span class="token punctuation">(</span>String t<span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token comment" spellcheck="true">// 设置title属性内容</span>         title <span class="token operator">=</span> t<span class="token punctuation">;</span>     <span class="token punctuation">}</span>     <span class="token comment" spellcheck="true">/**      * 设置或修改price属性内容      * @param p 接收要设置的数据      */</span>     <span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">setPrice</span><span class="token punctuation">(</span><span class="token keyword">double</span> p<span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token comment" spellcheck="true">// 设置price属性内容</span>         <span class="token keyword">if</span> <span class="token punctuation">(</span>p <span class="token operator">></span> <span class="token number">0.0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token comment" spellcheck="true">// 进行数据验证</span>            price <span class="token operator">=</span> p <span class="token punctuation">;</span>         <span class="token punctuation">}</span>     <span class="token punctuation">}</span>     <span class="token comment" spellcheck="true">/**      * 取得title属性内容      * @return title属性数据      */</span>     <span class="token keyword">public</span> String <span class="token function">getTitle</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token comment" spellcheck="true">// 取得title属性内容</span>         <span class="token keyword">return</span> title<span class="token punctuation">;</span>     <span class="token punctuation">}</span>     <span class="token comment" spellcheck="true">/**      * 取得price属性内容      * @return price属性数据      */</span>     <span class="token keyword">public</span> <span class="token keyword">double</span> <span class="token function">getPrice</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token comment" spellcheck="true">// 取得price属性内容</span>         <span class="token keyword">return</span> price<span class="token punctuation">;</span>     <span class="token punctuation">}</span>     <span class="token comment" spellcheck="true">/**      * 输出对象完整信息      */</span>     <span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">getInfo</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token comment" spellcheck="true">// 此方法将由对象调用</span>         System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"图书名称："</span> <span class="token operator">+</span> title <span class="token operator">+</span> <span class="token string">"，价格："</span> <span class="token operator">+</span> price<span class="token punctuation">)</span><span class="token punctuation">;</span>     <span class="token punctuation">}</span> <span class="token punctuation">}</span> <span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">TestDemo</span> <span class="token punctuation">{</span>     <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>         Book book <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Book</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 声明并实例化对象</span>         book<span class="token punctuation">.</span><span class="token function">setTitle</span><span class="token punctuation">(</span><span class="token string">"Java开发"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 设置属性内容</span>         book<span class="token punctuation">.</span><span class="token function">setPrice</span><span class="token punctuation">(</span><span class="token operator">-</span><span class="token number">89.9</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 设置属性内容</span>         book<span class="token punctuation">.</span><span class="token function">getInfo</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 调用方法</span>     <span class="token punctuation">}</span> <span class="token punctuation">}</span></code></pre>]]></content>
      
      
      
        <tags>
            
            <tag> Java </tag>
            
        </tags>
      
    </entry>
    
    
    
    <entry>
      <title>Numpy学习笔记</title>
      <link href="/2020/06/19/numpy-xue-xi-bi-ji/"/>
      <url>/2020/06/19/numpy-xue-xi-bi-ji/</url>
      
        <content type="html"><![CDATA[<p>[TOC]</p><h1 id="Numpy方法"><a href="#Numpy方法" class="headerlink" title="Numpy方法"></a>Numpy方法</h1><h3 id="np-ceil-x-y-限制元素范围"><a href="#np-ceil-x-y-限制元素范围" class="headerlink" title="np.ceil(x, y) 限制元素范围"></a>np.ceil(x, y) 限制元素范围</h3><ul><li>x 输入的数据</li><li>y float型，每个元素的上限</li></ul><pre class=" language-python"><code class="language-python">housing<span class="token punctuation">[</span><span class="token string">"income_cat"</span><span class="token punctuation">]</span> <span class="token operator">=</span> np<span class="token punctuation">.</span>ceil<span class="token punctuation">(</span>housing<span class="token punctuation">[</span><span class="token string">"median_income"</span><span class="token punctuation">]</span> <span class="token operator">/</span> <span class="token number">1.5</span><span class="token punctuation">)</span>     <span class="token comment" spellcheck="true"># 每个元素都除1.5</span></code></pre><h3 id="permutation-x-随机生成一个排列或返回一个range"><a href="#permutation-x-随机生成一个排列或返回一个range" class="headerlink" title="permutation(x) 随机生成一个排列或返回一个range"></a>permutation(x) 随机生成一个排列或返回一个range</h3><p>如果x是一个多维数组，则只会沿着它的第一个索引进行混洗。</p><pre class=" language-python"><code class="language-python"><span class="token keyword">import</span> numpy <span class="token keyword">as</span> npshuffle_index <span class="token operator">=</span> np<span class="token punctuation">.</span>random<span class="token punctuation">.</span>permutation<span class="token punctuation">(</span><span class="token number">60000</span><span class="token punctuation">)</span>X_train<span class="token punctuation">,</span> y_train <span class="token operator">=</span> X_train<span class="token punctuation">[</span>shuffle_index<span class="token punctuation">]</span><span class="token punctuation">,</span> y_train<span class="token punctuation">[</span>shuffle_index<span class="token punctuation">]</span></code></pre><h3 id="numpy-argmax-返回沿轴的最大值的索引"><a href="#numpy-argmax-返回沿轴的最大值的索引" class="headerlink" title="numpy.argmax() 返回沿轴的最大值的索引"></a>numpy.argmax() 返回沿轴的最大值的索引</h3><p>返回沿轴的最大值的索引。</p><pre class=" language-python"><code class="language-python"><span class="token comment" spellcheck="true"># some_digit_scores 内容</span><span class="token comment" spellcheck="true"># array([[-311402.62954431, -363517.28355739, -446449.5306454 ,</span><span class="token comment" spellcheck="true">#         -183226.61023518, -414337.15339485,  161855.74572176,</span><span class="token comment" spellcheck="true">#         -452576.39616343, -471957.14962573, -518542.33997148,</span><span class="token comment" spellcheck="true">#         -536774.63961222]])</span>np<span class="token punctuation">.</span>argmax<span class="token punctuation">(</span>some_digit_scores<span class="token punctuation">)</span><span class="token comment" spellcheck="true"># Out</span><span class="token comment" spellcheck="true"># 5</span></code></pre><ul><li>a : array_like; 输入数组</li><li>axis : int, optional; 默认情况下，索引是放在平面数组中，否则沿着指定的轴。</li><li>out : array, optional; 如果提供，结果将被插入到这个数组中。它应该是适当的形状和dtype。</li></ul><h3 id="np-linalg-inv-计算矩阵的逆"><a href="#np-linalg-inv-计算矩阵的逆" class="headerlink" title="np.linalg.inv() 计算矩阵的逆"></a>np.linalg.inv() 计算矩阵的逆</h3><pre class=" language-python"><code class="language-python">X_b <span class="token operator">=</span> np<span class="token punctuation">.</span>c_<span class="token punctuation">[</span>np<span class="token punctuation">.</span>ones<span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token number">100</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">,</span> X<span class="token punctuation">]</span>  <span class="token comment" spellcheck="true"># add x0 = 1 to each instance</span>theta_best <span class="token operator">=</span> np<span class="token punctuation">.</span>linalg<span class="token punctuation">.</span>inv<span class="token punctuation">(</span>X_b<span class="token punctuation">.</span>T<span class="token punctuation">.</span>dot<span class="token punctuation">(</span>X_b<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">.</span>dot<span class="token punctuation">(</span>X_b<span class="token punctuation">.</span>T<span class="token punctuation">)</span><span class="token punctuation">.</span>dot<span class="token punctuation">(</span>y<span class="token punctuation">)</span></code></pre><ul><li>a : (…, M, M) array_like；被求逆的矩阵</li></ul><h3 id="numpy-dot-a-b-out-None-计算两个数组的点积"><a href="#numpy-dot-a-b-out-None-计算两个数组的点积" class="headerlink" title="numpy.dot(a, b, out=None) 计算两个数组的点积"></a>numpy.dot(a, b, out=None) 计算两个数组的点积</h3><pre class=" language-python"><code class="language-python"><span class="token operator">>></span><span class="token operator">></span> np<span class="token punctuation">.</span>dot<span class="token punctuation">(</span><span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">)</span><span class="token number">12</span><span class="token comment" spellcheck="true"># Neither argument is complex-conjugated:</span><span class="token operator">>></span><span class="token operator">></span> np<span class="token punctuation">.</span>dot<span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">2j</span><span class="token punctuation">,</span> <span class="token number">3j</span><span class="token punctuation">]</span><span class="token punctuation">,</span> <span class="token punctuation">[</span><span class="token number">2j</span><span class="token punctuation">,</span> <span class="token number">3j</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">(</span><span class="token operator">-</span><span class="token number">13</span><span class="token operator">+</span><span class="token number">0j</span><span class="token punctuation">)</span><span class="token comment" spellcheck="true"># For 2-D arrays it is the matrix product:</span><span class="token operator">>></span><span class="token operator">></span> a <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">,</span> <span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">]</span><span class="token operator">>></span><span class="token operator">></span> b <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token punctuation">[</span><span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">,</span> <span class="token punctuation">[</span><span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">]</span><span class="token punctuation">]</span><span class="token operator">>></span><span class="token operator">></span> np<span class="token punctuation">.</span>dot<span class="token punctuation">(</span>a<span class="token punctuation">,</span> b<span class="token punctuation">)</span>array<span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token punctuation">[</span><span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">,</span>       <span class="token punctuation">[</span><span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">]</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token operator">>></span><span class="token operator">></span> a <span class="token operator">=</span> np<span class="token punctuation">.</span>arange<span class="token punctuation">(</span><span class="token number">3</span><span class="token operator">*</span><span class="token number">4</span><span class="token operator">*</span><span class="token number">5</span><span class="token operator">*</span><span class="token number">6</span><span class="token punctuation">)</span><span class="token punctuation">.</span>reshape<span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token number">3</span><span class="token punctuation">,</span><span class="token number">4</span><span class="token punctuation">,</span><span class="token number">5</span><span class="token punctuation">,</span><span class="token number">6</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token operator">>></span><span class="token operator">></span> b <span class="token operator">=</span> np<span class="token punctuation">.</span>arange<span class="token punctuation">(</span><span class="token number">3</span><span class="token operator">*</span><span class="token number">4</span><span class="token operator">*</span><span class="token number">5</span><span class="token operator">*</span><span class="token number">6</span><span class="token punctuation">)</span><span class="token punctuation">[</span><span class="token punctuation">:</span><span class="token punctuation">:</span><span class="token operator">-</span><span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">.</span>reshape<span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token number">5</span><span class="token punctuation">,</span><span class="token number">4</span><span class="token punctuation">,</span><span class="token number">6</span><span class="token punctuation">,</span><span class="token number">3</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token operator">>></span><span class="token operator">></span> np<span class="token punctuation">.</span>dot<span class="token punctuation">(</span>a<span class="token punctuation">,</span> b<span class="token punctuation">)</span><span class="token punctuation">[</span><span class="token number">2</span><span class="token punctuation">,</span><span class="token number">3</span><span class="token punctuation">,</span><span class="token number">2</span><span class="token punctuation">,</span><span class="token number">1</span><span class="token punctuation">,</span><span class="token number">2</span><span class="token punctuation">,</span><span class="token number">2</span><span class="token punctuation">]</span><span class="token number">499128</span><span class="token operator">>></span><span class="token operator">></span> sum<span class="token punctuation">(</span>a<span class="token punctuation">[</span><span class="token number">2</span><span class="token punctuation">,</span><span class="token number">3</span><span class="token punctuation">,</span><span class="token number">2</span><span class="token punctuation">,</span><span class="token punctuation">:</span><span class="token punctuation">]</span> <span class="token operator">*</span> b<span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span><span class="token number">2</span><span class="token punctuation">,</span><span class="token punctuation">:</span><span class="token punctuation">,</span><span class="token number">2</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token number">499128</span></code></pre><ul><li>a : array_like；First argument.</li><li>b : array_like；Second argument.</li></ul><h3 id="numpy-ndarray-T-计算矩阵的转置"><a href="#numpy-ndarray-T-计算矩阵的转置" class="headerlink" title="numpy.ndarray.T() 计算矩阵的转置"></a>numpy.ndarray.T() 计算矩阵的转置</h3><p>与<code>self.transpose()</code>相同，如果<code>self.ndim &lt; 2</code>则返回它自身。</p><pre class=" language-python"><code class="language-python"><span class="token operator">>></span><span class="token operator">></span> x <span class="token operator">=</span> np<span class="token punctuation">.</span>array<span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">.</span><span class="token punctuation">,</span><span class="token number">2</span><span class="token punctuation">.</span><span class="token punctuation">]</span><span class="token punctuation">,</span><span class="token punctuation">[</span><span class="token number">3</span><span class="token punctuation">.</span><span class="token punctuation">,</span><span class="token number">4</span><span class="token punctuation">.</span><span class="token punctuation">]</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token operator">>></span><span class="token operator">></span> xarray<span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token punctuation">[</span> <span class="token number">1</span><span class="token punctuation">.</span><span class="token punctuation">,</span>  <span class="token number">2</span><span class="token punctuation">.</span><span class="token punctuation">]</span><span class="token punctuation">,</span>       <span class="token punctuation">[</span> <span class="token number">3</span><span class="token punctuation">.</span><span class="token punctuation">,</span>  <span class="token number">4</span><span class="token punctuation">.</span><span class="token punctuation">]</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token operator">>></span><span class="token operator">></span> x<span class="token punctuation">.</span>Tarray<span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token punctuation">[</span> <span class="token number">1</span><span class="token punctuation">.</span><span class="token punctuation">,</span>  <span class="token number">3</span><span class="token punctuation">.</span><span class="token punctuation">]</span><span class="token punctuation">,</span>       <span class="token punctuation">[</span> <span class="token number">2</span><span class="token punctuation">.</span><span class="token punctuation">,</span>  <span class="token number">4</span><span class="token punctuation">.</span><span class="token punctuation">]</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token operator">>></span><span class="token operator">></span> x <span class="token operator">=</span> np<span class="token punctuation">.</span>array<span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">.</span><span class="token punctuation">,</span><span class="token number">2</span><span class="token punctuation">.</span><span class="token punctuation">,</span><span class="token number">3</span><span class="token punctuation">.</span><span class="token punctuation">,</span><span class="token number">4</span><span class="token punctuation">.</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token operator">>></span><span class="token operator">></span> xarray<span class="token punctuation">(</span><span class="token punctuation">[</span> <span class="token number">1</span><span class="token punctuation">.</span><span class="token punctuation">,</span>  <span class="token number">2</span><span class="token punctuation">.</span><span class="token punctuation">,</span>  <span class="token number">3</span><span class="token punctuation">.</span><span class="token punctuation">,</span>  <span class="token number">4</span><span class="token punctuation">.</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token operator">>></span><span class="token operator">></span> x<span class="token punctuation">.</span>Tarray<span class="token punctuation">(</span><span class="token punctuation">[</span> <span class="token number">1</span><span class="token punctuation">.</span><span class="token punctuation">,</span>  <span class="token number">2</span><span class="token punctuation">.</span><span class="token punctuation">,</span>  <span class="token number">3</span><span class="token punctuation">.</span><span class="token punctuation">,</span>  <span class="token number">4</span><span class="token punctuation">.</span><span class="token punctuation">]</span><span class="token punctuation">)</span></code></pre><h3 id="numpy-random-seed-生成器种子"><a href="#numpy-random-seed-生成器种子" class="headerlink" title="numpy.random.seed() 生成器种子"></a>numpy.random.seed() 生成器种子</h3><p>该方法由<code>RandomState</code>初始化，它可以被重新设置。</p><pre class=" language-python"><code class="language-python">np<span class="token punctuation">.</span>random<span class="token punctuation">.</span>seed<span class="token punctuation">(</span><span class="token number">42</span><span class="token punctuation">)</span>theta <span class="token operator">=</span> np<span class="token punctuation">.</span>random<span class="token punctuation">.</span>randn<span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">,</span><span class="token number">1</span><span class="token punctuation">)</span>  <span class="token comment" spellcheck="true"># random initialization</span></code></pre><ul><li>seed : int or array_like, optional；必须为32位无符号整数。</li></ul><h3 id="numpy-random-randn-从标准正太分布返回样本"><a href="#numpy-random-randn-从标准正太分布返回样本" class="headerlink" title="numpy.random.randn() 从标准正太分布返回样本"></a>numpy.random.randn() 从标准正太分布返回样本</h3><pre class=" language-python"><code class="language-python"><span class="token operator">>></span><span class="token operator">></span> theta <span class="token operator">=</span> np<span class="token punctuation">.</span>random<span class="token punctuation">.</span>randn<span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">,</span><span class="token number">1</span><span class="token punctuation">)</span>array<span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token punctuation">[</span> <span class="token number">4.21509616</span><span class="token punctuation">]</span><span class="token punctuation">,</span>       <span class="token punctuation">[</span> <span class="token number">2.77011339</span><span class="token punctuation">]</span><span class="token punctuation">]</span><span class="token punctuation">)</span></code></pre><h6 id="参数"><a href="#参数" class="headerlink" title="参数"></a>参数</h6><ul><li>d0, d1, …, dn : int, optional；返回的数组维度，应该都是正值。如果没有给出，将返回一个Python float值。</li></ul><h6 id="返回值"><a href="#返回值" class="headerlink" title="返回值"></a>返回值</h6><ul><li>Z : ndarray or float；一个经过标准正态分布抽样的，<code>(d0, d1, ..., dn)</code>维度的浮点数组。</li></ul><h3 id="numpy-array-创建一个数组"><a href="#numpy-array-创建一个数组" class="headerlink" title="numpy.array() 创建一个数组"></a>numpy.array() 创建一个数组</h3><pre class=" language-python"><code class="language-python">theta_path_bgd <span class="token operator">=</span> np<span class="token punctuation">.</span>array<span class="token punctuation">(</span>theta_path_bgd<span class="token punctuation">)</span>theta_path_sgd <span class="token operator">=</span> np<span class="token punctuation">.</span>array<span class="token punctuation">(</span>theta_path_sgd<span class="token punctuation">)</span>theta_path_mgd <span class="token operator">=</span> np<span class="token punctuation">.</span>array<span class="token punctuation">(</span>theta_path_mgd<span class="token punctuation">)</span></code></pre><ul><li>object : array_like</li><li>dtype : data-type, optional</li></ul><h3 id="numpy-random-rand-nmbsp-生成给定shap的随机值"><a href="#numpy-random-rand-nmbsp-生成给定shap的随机值" class="headerlink" title="numpy.random.rand()&nmbsp;生成给定shap的随机值"></a>numpy.random.rand()&nmbsp;生成给定shap的随机值</h3><pre class=" language-python"><code class="language-python">m <span class="token operator">=</span> <span class="token number">100</span>X <span class="token operator">=</span> <span class="token number">6</span> <span class="token operator">*</span> np<span class="token punctuation">.</span>random<span class="token punctuation">.</span>rand<span class="token punctuation">(</span>m<span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">)</span> <span class="token operator">-</span> <span class="token number">3</span>y <span class="token operator">=</span> <span class="token number">0.5</span> <span class="token operator">*</span> X<span class="token operator">**</span><span class="token number">2</span> <span class="token operator">+</span> X <span class="token operator">+</span> <span class="token number">2</span> <span class="token operator">+</span> np<span class="token punctuation">.</span>random<span class="token punctuation">.</span>randn<span class="token punctuation">(</span>m<span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">)</span><span class="token operator">>></span><span class="token operator">></span> np<span class="token punctuation">.</span>random<span class="token punctuation">.</span>rand<span class="token punctuation">(</span><span class="token number">3</span><span class="token punctuation">,</span><span class="token number">2</span><span class="token punctuation">)</span>array<span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token punctuation">[</span> <span class="token number">0.14022471</span><span class="token punctuation">,</span>  <span class="token number">0.96360618</span><span class="token punctuation">]</span><span class="token punctuation">,</span>  <span class="token comment" spellcheck="true">#random</span>       <span class="token punctuation">[</span> <span class="token number">0.37601032</span><span class="token punctuation">,</span>  <span class="token number">0.25528411</span><span class="token punctuation">]</span><span class="token punctuation">,</span>  <span class="token comment" spellcheck="true">#random</span>       <span class="token punctuation">[</span> <span class="token number">0.49313049</span><span class="token punctuation">,</span>  <span class="token number">0.94909878</span><span class="token punctuation">]</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token comment" spellcheck="true">#random</span></code></pre><ul><li>d0, d1, …, dn : int, optional；返回的数组维度，必须是正值。如果为空，则返回一个Python float值。</li></ul><h3 id="numpy-linspace-在指定区间返回间隔均匀的样本-start-stop"><a href="#numpy-linspace-在指定区间返回间隔均匀的样本-start-stop" class="headerlink" title="numpy.linspace() 在指定区间返回间隔均匀的样本[start, stop]"></a>numpy.linspace() 在指定区间返回间隔均匀的样本[start, stop]</h3><pre class=" language-python"><code class="language-python">X_new<span class="token operator">=</span>np<span class="token punctuation">.</span>linspace<span class="token punctuation">(</span><span class="token operator">-</span><span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">100</span><span class="token punctuation">)</span><span class="token punctuation">.</span>reshape<span class="token punctuation">(</span><span class="token number">100</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">)</span>X_new_poly <span class="token operator">=</span> poly_features<span class="token punctuation">.</span>transform<span class="token punctuation">(</span>X_new<span class="token punctuation">)</span>y_new <span class="token operator">=</span> lin_reg<span class="token punctuation">.</span>predict<span class="token punctuation">(</span>X_new_poly<span class="token punctuation">)</span>plt<span class="token punctuation">.</span>plot<span class="token punctuation">(</span>X<span class="token punctuation">,</span> y<span class="token punctuation">,</span> <span class="token string">"b."</span><span class="token punctuation">)</span>plt<span class="token punctuation">.</span>plot<span class="token punctuation">(</span>X_new<span class="token punctuation">,</span> y_new<span class="token punctuation">,</span> <span class="token string">"r-"</span><span class="token punctuation">,</span> linewidth<span class="token operator">=</span><span class="token number">2</span><span class="token punctuation">,</span> label<span class="token operator">=</span><span class="token string">"Predictions"</span><span class="token punctuation">)</span>plt<span class="token punctuation">.</span>xlabel<span class="token punctuation">(</span><span class="token string">"$x_1$"</span><span class="token punctuation">,</span> fontsize<span class="token operator">=</span><span class="token number">18</span><span class="token punctuation">)</span>plt<span class="token punctuation">.</span>ylabel<span class="token punctuation">(</span><span class="token string">"$y$"</span><span class="token punctuation">,</span> rotation<span class="token operator">=</span><span class="token number">0</span><span class="token punctuation">,</span> fontsize<span class="token operator">=</span><span class="token number">18</span><span class="token punctuation">)</span>plt<span class="token punctuation">.</span>legend<span class="token punctuation">(</span>loc<span class="token operator">=</span><span class="token string">"upper left"</span><span class="token punctuation">,</span> fontsize<span class="token operator">=</span><span class="token number">14</span><span class="token punctuation">)</span>plt<span class="token punctuation">.</span>axis<span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token operator">-</span><span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">10</span><span class="token punctuation">]</span><span class="token punctuation">)</span>save_fig<span class="token punctuation">(</span><span class="token string">"quadratic_predictions_plot"</span><span class="token punctuation">)</span>plt<span class="token punctuation">.</span>show<span class="token punctuation">(</span><span class="token punctuation">)</span></code></pre><ul><li>start : scalar；序列的起始值</li><li>stop : scalar；序列的结束值</li><li>num : int, optional；要生成的样本数量，默认为50个。</li><li>endpoint : bool, optional；若为True则包括结束值，否则不包括结束值，即[start, stop)区间。默认为True。</li><li>dtype : dtype, optional；输出数组的类型，若未给出则从输入数据推断类型。</li></ul><h3 id="meshgrid-从坐标向量返回坐标矩阵"><a href="#meshgrid-从坐标向量返回坐标矩阵" class="headerlink" title="meshgrid() 从坐标向量返回坐标矩阵"></a>meshgrid() 从坐标向量返回坐标矩阵</h3><pre class=" language-python"><code class="language-python"><span class="token operator">>></span><span class="token operator">></span> nx<span class="token punctuation">,</span> ny <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">)</span><span class="token operator">>></span><span class="token operator">></span> x <span class="token operator">=</span> np<span class="token punctuation">.</span>linspace<span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> nx<span class="token punctuation">)</span><span class="token operator">>></span><span class="token operator">></span> y <span class="token operator">=</span> np<span class="token punctuation">.</span>linspace<span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> ny<span class="token punctuation">)</span><span class="token operator">>></span><span class="token operator">></span> xv<span class="token punctuation">,</span> yv <span class="token operator">=</span> np<span class="token punctuation">.</span>meshgrid<span class="token punctuation">(</span>x<span class="token punctuation">,</span> y<span class="token punctuation">)</span><span class="token operator">>></span><span class="token operator">></span> xvarray<span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token punctuation">[</span> <span class="token number">0</span><span class="token punctuation">.</span> <span class="token punctuation">,</span>  <span class="token number">0.5</span><span class="token punctuation">,</span>  <span class="token number">1</span><span class="token punctuation">.</span> <span class="token punctuation">]</span><span class="token punctuation">,</span>       <span class="token punctuation">[</span> <span class="token number">0</span><span class="token punctuation">.</span> <span class="token punctuation">,</span>  <span class="token number">0.5</span><span class="token punctuation">,</span>  <span class="token number">1</span><span class="token punctuation">.</span> <span class="token punctuation">]</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token operator">>></span><span class="token operator">></span> yvarray<span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token punctuation">[</span> <span class="token number">0</span><span class="token punctuation">.</span><span class="token punctuation">,</span>  <span class="token number">0</span><span class="token punctuation">.</span><span class="token punctuation">,</span>  <span class="token number">0</span><span class="token punctuation">.</span><span class="token punctuation">]</span><span class="token punctuation">,</span>       <span class="token punctuation">[</span> <span class="token number">1</span><span class="token punctuation">.</span><span class="token punctuation">,</span>  <span class="token number">1</span><span class="token punctuation">.</span><span class="token punctuation">,</span>  <span class="token number">1</span><span class="token punctuation">.</span><span class="token punctuation">]</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token operator">>></span><span class="token operator">></span> xv<span class="token punctuation">,</span> yv <span class="token operator">=</span> np<span class="token punctuation">.</span>meshgrid<span class="token punctuation">(</span>x<span class="token punctuation">,</span> y<span class="token punctuation">,</span> sparse<span class="token operator">=</span><span class="token boolean">True</span><span class="token punctuation">)</span>  <span class="token comment" spellcheck="true"># make sparse output arrays</span><span class="token operator">>></span><span class="token operator">></span> xvarray<span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token punctuation">[</span> <span class="token number">0</span><span class="token punctuation">.</span> <span class="token punctuation">,</span>  <span class="token number">0.5</span><span class="token punctuation">,</span>  <span class="token number">1</span><span class="token punctuation">.</span> <span class="token punctuation">]</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token operator">>></span><span class="token operator">></span> yvarray<span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token punctuation">[</span> <span class="token number">0</span><span class="token punctuation">.</span><span class="token punctuation">]</span><span class="token punctuation">,</span>       <span class="token punctuation">[</span> <span class="token number">1</span><span class="token punctuation">.</span><span class="token punctuation">]</span><span class="token punctuation">]</span><span class="token punctuation">)</span></code></pre><ul><li>x1, x2,…, xn : array_like；代表网格坐标的一维数组。</li><li>indexing : {‘xy’, ‘ij’}, optional；输出的笛卡儿（’xy’，默认）或矩阵（’ij’）索引。</li><li>sparse : bool, optional；如果为True则返回稀疏矩阵以减少内存，默认为False。</li></ul><h3 id="norm-矩阵或向量范数"><a href="#norm-矩阵或向量范数" class="headerlink" title="norm() 矩阵或向量范数"></a>norm() 矩阵或向量范数</h3><pre class=" language-python"><code class="language-python">t1a<span class="token punctuation">,</span> t1b<span class="token punctuation">,</span> t2a<span class="token punctuation">,</span> t2b <span class="token operator">=</span> <span class="token operator">-</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token operator">-</span><span class="token number">1.5</span><span class="token punctuation">,</span> <span class="token number">1.5</span><span class="token comment" spellcheck="true"># ignoring bias term</span>t1s <span class="token operator">=</span> np<span class="token punctuation">.</span>linspace<span class="token punctuation">(</span>t1a<span class="token punctuation">,</span> t1b<span class="token punctuation">,</span> <span class="token number">500</span><span class="token punctuation">)</span>t2s <span class="token operator">=</span> np<span class="token punctuation">.</span>linspace<span class="token punctuation">(</span>t2a<span class="token punctuation">,</span> t2b<span class="token punctuation">,</span> <span class="token number">500</span><span class="token punctuation">)</span>t1<span class="token punctuation">,</span> t2 <span class="token operator">=</span> np<span class="token punctuation">.</span>meshgrid<span class="token punctuation">(</span>t1s<span class="token punctuation">,</span> t2s<span class="token punctuation">)</span>T <span class="token operator">=</span> np<span class="token punctuation">.</span>c_<span class="token punctuation">[</span>t1<span class="token punctuation">.</span>ravel<span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span> t2<span class="token punctuation">.</span>ravel<span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">]</span>Xr <span class="token operator">=</span> np<span class="token punctuation">.</span>array<span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token punctuation">[</span><span class="token operator">-</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">,</span> <span class="token punctuation">[</span><span class="token operator">-</span><span class="token number">0.3</span><span class="token punctuation">,</span> <span class="token operator">-</span><span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">,</span> <span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">0.1</span><span class="token punctuation">]</span><span class="token punctuation">]</span><span class="token punctuation">)</span>yr <span class="token operator">=</span> <span class="token number">2</span> <span class="token operator">*</span> Xr<span class="token punctuation">[</span><span class="token punctuation">:</span><span class="token punctuation">,</span> <span class="token punctuation">:</span><span class="token number">1</span><span class="token punctuation">]</span> <span class="token operator">+</span> <span class="token number">0.5</span> <span class="token operator">*</span> Xr<span class="token punctuation">[</span><span class="token punctuation">:</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">:</span><span class="token punctuation">]</span>J <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token number">1</span><span class="token operator">/</span>len<span class="token punctuation">(</span>Xr<span class="token punctuation">)</span> <span class="token operator">*</span> np<span class="token punctuation">.</span>sum<span class="token punctuation">(</span><span class="token punctuation">(</span>T<span class="token punctuation">.</span>dot<span class="token punctuation">(</span>Xr<span class="token punctuation">.</span>T<span class="token punctuation">)</span> <span class="token operator">-</span> yr<span class="token punctuation">.</span>T<span class="token punctuation">)</span><span class="token operator">**</span><span class="token number">2</span><span class="token punctuation">,</span> axis<span class="token operator">=</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">.</span>reshape<span class="token punctuation">(</span>t1<span class="token punctuation">.</span>shape<span class="token punctuation">)</span>N1 <span class="token operator">=</span> np<span class="token punctuation">.</span>linalg<span class="token punctuation">.</span>norm<span class="token punctuation">(</span>T<span class="token punctuation">,</span> ord<span class="token operator">=</span><span class="token number">1</span><span class="token punctuation">,</span> axis<span class="token operator">=</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">.</span>reshape<span class="token punctuation">(</span>t1<span class="token punctuation">.</span>shape<span class="token punctuation">)</span>N2 <span class="token operator">=</span> np<span class="token punctuation">.</span>linalg<span class="token punctuation">.</span>norm<span class="token punctuation">(</span>T<span class="token punctuation">,</span> ord<span class="token operator">=</span><span class="token number">2</span><span class="token punctuation">,</span> axis<span class="token operator">=</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">.</span>reshape<span class="token punctuation">(</span>t1<span class="token punctuation">.</span>shape<span class="token punctuation">)</span>t_min_idx <span class="token operator">=</span> np<span class="token punctuation">.</span>unravel_index<span class="token punctuation">(</span>np<span class="token punctuation">.</span>argmin<span class="token punctuation">(</span>J<span class="token punctuation">)</span><span class="token punctuation">,</span> J<span class="token punctuation">.</span>shape<span class="token punctuation">)</span>t1_min<span class="token punctuation">,</span> t2_min <span class="token operator">=</span> t1<span class="token punctuation">[</span>t_min_idx<span class="token punctuation">]</span><span class="token punctuation">,</span> t2<span class="token punctuation">[</span>t_min_idx<span class="token punctuation">]</span>t_init <span class="token operator">=</span> np<span class="token punctuation">.</span>array<span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token punctuation">[</span><span class="token number">0.25</span><span class="token punctuation">]</span><span class="token punctuation">,</span> <span class="token punctuation">[</span><span class="token operator">-</span><span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">]</span><span class="token punctuation">)</span></code></pre><ul><li>x : array_like；输入的数组，如果<code>axis</code>是None，则<code>x</code>必须是1-D或2-D。</li><li>ord : {non-zero int, inf, -inf, ‘fro’, ‘nuc’}, optional；范数的顺序，inf表示numpy的inf对象。</li><li>axis : {int, 2-tuple of ints, None}, optional</li><li>keepdims : bool, optional</li></ul><p>以下范数可以被计算：</p><table><thead><tr><th>ord</th><th>norm for matrices</th><th>norm for vectors</th></tr></thead><tbody><tr><td>None</td><td>Frobenius norm</td><td>2-norm</td></tr><tr><td>‘fro’</td><td>Frobenius norm</td><td>–</td></tr><tr><td>‘nuc’</td><td>nuclear norm</td><td>–</td></tr><tr><td>inf</td><td>max(sum(abs(x), axis=1))</td><td>max(abs(x))</td></tr><tr><td>-inf</td><td>min(sum(abs(x), axis=1))</td><td>min(abs(x))</td></tr><tr><td>0</td><td>–</td><td>sum(x != 0)</td></tr><tr><td>1</td><td>max(sum(abs(x), axis=0))</td><td>as below</td></tr><tr><td>-1</td><td>min(sum(abs(x), axis=0))</td><td>as below</td></tr><tr><td>2</td><td>2-norm (largest sing. value)</td><td>as below</td></tr><tr><td>-2</td><td>smallest singular value</td><td>as below</td></tr><tr><td>other</td><td>–</td><td>sum(abs(x)<strong>ord)</strong>(1./ord)</td></tr></tbody></table><p>对于<code>ord &lt;= 0</code>的值，它严格来说不是数学规范的范数，但它作为数值目的任然有用。</p><h3 id="unravel-index-将平面索引或平面索引数组转换为坐标数组的元组"><a href="#unravel-index-将平面索引或平面索引数组转换为坐标数组的元组" class="headerlink" title="unravel_index() 将平面索引或平面索引数组转换为坐标数组的元组"></a>unravel_index() 将平面索引或平面索引数组转换为坐标数组的元组</h3><pre class=" language-python"><code class="language-python"><span class="token operator">>></span><span class="token operator">></span> np<span class="token punctuation">.</span>unravel_index<span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">22</span><span class="token punctuation">,</span> <span class="token number">41</span><span class="token punctuation">,</span> <span class="token number">37</span><span class="token punctuation">]</span><span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token number">7</span><span class="token punctuation">,</span><span class="token number">6</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">(</span>array<span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">6</span><span class="token punctuation">,</span> <span class="token number">6</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">,</span> array<span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token operator">>></span><span class="token operator">></span> np<span class="token punctuation">.</span>unravel_index<span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">31</span><span class="token punctuation">,</span> <span class="token number">41</span><span class="token punctuation">,</span> <span class="token number">13</span><span class="token punctuation">]</span><span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token number">7</span><span class="token punctuation">,</span><span class="token number">6</span><span class="token punctuation">)</span><span class="token punctuation">,</span> order<span class="token operator">=</span><span class="token string">'F'</span><span class="token punctuation">)</span><span class="token punctuation">(</span>array<span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">6</span><span class="token punctuation">,</span> <span class="token number">6</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">,</span> array<span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token operator">>></span><span class="token operator">></span> np<span class="token punctuation">.</span>unravel_index<span class="token punctuation">(</span><span class="token number">1621</span><span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token number">6</span><span class="token punctuation">,</span><span class="token number">7</span><span class="token punctuation">,</span><span class="token number">8</span><span class="token punctuation">,</span><span class="token number">9</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">(</span><span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">)</span></code></pre><ul><li>indices : array_like；一个整数数组，其元素是索引到维数组dims的平坦版本中。</li><li>dims : tuple of ints；用于分解索引的数组的形状。</li><li>order : {‘C’, ‘F’}, optional；决定<code>indices</code>应该按row-major (C-style) or column-major (Fortran-style) 顺序。</li></ul><h3 id="mean-计算沿指定轴的算术平均值"><a href="#mean-计算沿指定轴的算术平均值" class="headerlink" title="mean() 计算沿指定轴的算术平均值"></a>mean() 计算沿指定轴的算术平均值</h3><pre class=" language-python"><code class="language-python"><span class="token operator">>></span><span class="token operator">></span> a <span class="token operator">=</span> np<span class="token punctuation">.</span>array<span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">]</span><span class="token punctuation">,</span> <span class="token punctuation">[</span><span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">]</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token operator">>></span><span class="token operator">></span> np<span class="token punctuation">.</span>mean<span class="token punctuation">(</span>a<span class="token punctuation">)</span><span class="token number">2.5</span><span class="token operator">>></span><span class="token operator">></span> np<span class="token punctuation">.</span>mean<span class="token punctuation">(</span>a<span class="token punctuation">,</span> axis<span class="token operator">=</span><span class="token number">0</span><span class="token punctuation">)</span>array<span class="token punctuation">(</span><span class="token punctuation">[</span> <span class="token number">2</span><span class="token punctuation">.</span><span class="token punctuation">,</span>  <span class="token number">3</span><span class="token punctuation">.</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token operator">>></span><span class="token operator">></span> np<span class="token punctuation">.</span>mean<span class="token punctuation">(</span>a<span class="token punctuation">,</span> axis<span class="token operator">=</span><span class="token number">1</span><span class="token punctuation">)</span>array<span class="token punctuation">(</span><span class="token punctuation">[</span> <span class="token number">1.5</span><span class="token punctuation">,</span>  <span class="token number">3.5</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token operator">>></span><span class="token operator">></span> a <span class="token operator">=</span> np<span class="token punctuation">.</span>zeros<span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">512</span><span class="token operator">*</span><span class="token number">512</span><span class="token punctuation">)</span><span class="token punctuation">,</span> dtype<span class="token operator">=</span>np<span class="token punctuation">.</span>float32<span class="token punctuation">)</span><span class="token operator">>></span><span class="token operator">></span> a<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">,</span> <span class="token punctuation">:</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">1.0</span><span class="token operator">>></span><span class="token operator">></span> a<span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token punctuation">:</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">0.1</span><span class="token operator">>></span><span class="token operator">></span> np<span class="token punctuation">.</span>mean<span class="token punctuation">(</span>a<span class="token punctuation">)</span><span class="token number">0.54999924</span></code></pre><ul><li>a : array_like；包含要求平均值的数组，如果不是数组，则尝试进行转换。</li><li>axis : None or int or tuple of ints, optional；计算平均值的轴，默认计算扁平数组。</li><li>dtype : data-type, optional；用于计算平均值的类型。</li><li>out : ndarray, optional</li></ul>]]></content>
      
      
      
        <tags>
            
            <tag> python </tag>
            
            <tag> Machine Learning </tag>
            
        </tags>
      
    </entry>
    
    
    
    <entry>
      <title>Pandas学习笔记</title>
      <link href="/2020/06/18/pandas-xue-xi-bi-ji/"/>
      <url>/2020/06/18/pandas-xue-xi-bi-ji/</url>
      
        <content type="html"><![CDATA[<p>[TOC]</p><h2 id="Pandas方法"><a href="#Pandas方法" class="headerlink" title="Pandas方法"></a>Pandas方法</h2><p>使用pandas首先要导入pandas包。</p><pre class=" language-python"><code class="language-python"><span class="token keyword">import</span> pandas <span class="token keyword">as</span> pd  <span class="token operator">//</span>标准的导入pandas的代码</code></pre><h3 id="读入csv文件"><a href="#读入csv文件" class="headerlink" title="读入csv文件"></a>读入csv文件</h3><pre class=" language-python"><code class="language-python">trainData <span class="token operator">=</span> pd<span class="token punctuation">.</span>read_csv<span class="token punctuation">(</span><span class="token string">"./Data/train.csv"</span><span class="token punctuation">)</span> <span class="token operator">//</span><span class="token punctuation">.</span><span class="token operator">/</span>Data<span class="token operator">/</span>   表示路径，train表示文件名</code></pre><h3 id="标题获取文件中的前5行数据"><a href="#标题获取文件中的前5行数据" class="headerlink" title="标题获取文件中的前5行数据"></a>标题获取文件中的前5行数据</h3><pre class=" language-python"><code class="language-python">trainData<span class="token punctuation">.</span>head<span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">//</span><span class="token punctuation">.</span>head<span class="token punctuation">(</span><span class="token punctuation">)</span>是pandas中的一个方法，可以获取文件中的前<span class="token number">5</span>行数据</code></pre><p><img src="https://img-blog.csdnimg.cn/20190521193906796.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mzg5NTQ4Mg==,size_16,color_FFFFFF,t_70" alt="在这里插入图片描述"></p><h3 id="info-迅速获取数据描述"><a href="#info-迅速获取数据描述" class="headerlink" title="info() 迅速获取数据描述"></a>info() 迅速获取数据描述</h3><pre class=" language-python"><code class="language-python">trainData<span class="token punctuation">.</span>info<span class="token punctuation">(</span><span class="token punctuation">)</span>  <span class="token operator">//</span> 方法就不具体介绍了   下面给出运行结果<span class="token operator">//</span><span class="token operator">//</span><span class="token operator">//</span><span class="token operator">//</span><span class="token operator">//</span><span class="token operator">//</span><span class="token operator">//</span>    运行结果<span class="token operator">&lt;</span><span class="token keyword">class</span> <span class="token string">'pandas.core.frame.DataFrame'</span><span class="token operator">></span>RangeIndex<span class="token punctuation">:</span> <span class="token number">891</span> entries<span class="token punctuation">,</span> <span class="token number">0</span> to <span class="token number">890</span>Data columns <span class="token punctuation">(</span>total <span class="token number">10</span> columns<span class="token punctuation">)</span><span class="token punctuation">:</span>Pclass      <span class="token number">891</span> non<span class="token operator">-</span>null int64Name        <span class="token number">891</span> non<span class="token operator">-</span>null objectSex         <span class="token number">891</span> non<span class="token operator">-</span>null objectAge         <span class="token number">714</span> non<span class="token operator">-</span>null float64SibSp       <span class="token number">891</span> non<span class="token operator">-</span>null int64Parch       <span class="token number">891</span> non<span class="token operator">-</span>null int64Ticket      <span class="token number">891</span> non<span class="token operator">-</span>null objectFare        <span class="token number">891</span> non<span class="token operator">-</span>null float64Cabin       <span class="token number">204</span> non<span class="token operator">-</span>null objectEmbarked    <span class="token number">889</span> non<span class="token operator">-</span>null objectdtypes<span class="token punctuation">:</span> float64<span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">,</span> int64<span class="token punctuation">(</span><span class="token number">3</span><span class="token punctuation">)</span><span class="token punctuation">,</span> object<span class="token punctuation">(</span><span class="token number">5</span><span class="token punctuation">)</span>memory usage<span class="token punctuation">:</span> <span class="token number">69.7</span><span class="token operator">+</span> KB</code></pre><p><img src="https://img-blog.csdnimg.cn/20190915110156432.PNG?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mzg5NTQ4Mg==,size_16,color_FFFFFF,t_70" alt="在这里插入图片描述"></p><h3 id="drop"><a href="#drop" class="headerlink" title=".drop( , , )"></a>.drop( , , )</h3><pre class=" language-python"><code class="language-python"><span class="token comment" spellcheck="true">#删除name</span>allData<span class="token punctuation">.</span>drop<span class="token punctuation">(</span><span class="token string">"Name"</span><span class="token punctuation">,</span>axis<span class="token operator">=</span><span class="token number">1</span><span class="token punctuation">,</span>inplace<span class="token operator">=</span><span class="token boolean">True</span><span class="token punctuation">)</span>  <span class="token operator">//</span>第一个参数为要删除的内容，第二第三个参数的形式固定</code></pre><h3 id="替换文件中的内容"><a href="#替换文件中的内容" class="headerlink" title="替换文件中的内容"></a>替换文件中的内容</h3><pre class=" language-python"><code class="language-python"><span class="token comment" spellcheck="true">#可以考虑替换为出现的次数</span>allData<span class="token punctuation">[</span><span class="token string">'SibSp'</span><span class="token punctuation">]</span><span class="token punctuation">.</span>value_counts<span class="token punctuation">(</span><span class="token punctuation">)</span>   <span class="token operator">//</span> 替换SibSp中缺失的数据为出现的次数<span class="token operator">//</span><span class="token operator">//</span><span class="token operator">//</span><span class="token operator">//</span><span class="token operator">//</span><span class="token operator">//</span><span class="token operator">//</span><span class="token operator">/</span>运行结果<span class="token number">0</span>    <span class="token number">891</span><span class="token number">1</span>    <span class="token number">319</span><span class="token number">2</span>     <span class="token number">42</span><span class="token number">4</span>     <span class="token number">22</span><span class="token number">3</span>     <span class="token number">20</span><span class="token number">8</span>      <span class="token number">9</span><span class="token number">5</span>      <span class="token number">6</span>Name<span class="token punctuation">:</span> SibSp<span class="token punctuation">,</span> dtype<span class="token punctuation">:</span> int64</code></pre><h3 id="合并两个文件中的内容"><a href="#合并两个文件中的内容" class="headerlink" title="合并两个文件中的内容"></a>合并两个文件中的内容</h3><pre class=" language-python"><code class="language-python">allData <span class="token operator">=</span> pd<span class="token punctuation">.</span>concat<span class="token punctuation">(</span><span class="token punctuation">[</span>trainData<span class="token punctuation">,</span>testData<span class="token punctuation">]</span><span class="token punctuation">,</span>axis<span class="token operator">=</span><span class="token number">0</span><span class="token punctuation">,</span>ignore_index<span class="token operator">=</span><span class="token boolean">True</span><span class="token punctuation">)</span>  <span class="token operator">//</span>第一个参数为两个文件名，第二第三个参数格式相同</code></pre><h3 id="pd-set-option-设置指定的值"><a href="#pd-set-option-设置指定的值" class="headerlink" title="pd.set_option() 设置指定的值"></a>pd.set_option() 设置指定的值</h3><pre class=" language-python"><code class="language-python">pd<span class="token punctuation">.</span>setoption<span class="token punctuation">(</span><span class="token string">'max_rows'</span><span class="token punctuation">,</span><span class="token number">7</span><span class="token punctuation">)</span>  <span class="token operator">//</span><span class="token operator">//</span><span class="token operator">//</span>设置最大的行数</code></pre><h3 id="value-counts-获取每个值出现的次数"><a href="#value-counts-获取每个值出现的次数" class="headerlink" title="value_counts()   获取每个值出现的次数"></a>value_counts()   获取每个值出现的次数</h3><pre class=" language-python"><code class="language-python">trainData<span class="token punctuation">[</span><span class="token string">'Pclass'</span><span class="token punctuation">]</span><span class="token punctuation">.</span>value_counts<span class="token punctuation">(</span><span class="token punctuation">)</span></code></pre><h3 id="fillna-用指定方法填充"><a href="#fillna-用指定方法填充" class="headerlink" title="fillna()   用指定方法填充"></a>fillna()   用指定方法填充</h3><pre class=" language-python"><code class="language-python">age <span class="token operator">=</span> trainData<span class="token punctuation">[</span><span class="token string">'Age'</span><span class="token punctuation">]</span>age <span class="token operator">=</span> age<span class="token punctuation">.</span>fillna<span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">)</span>   <span class="token operator">//</span><span class="token operator">//</span>将年龄用<span class="token number">0</span>来填充</code></pre><h3 id="客串seaborn中的一个方法-distplot-age-画出age的树状图"><a href="#客串seaborn中的一个方法-distplot-age-画出age的树状图" class="headerlink" title="客串seaborn中的一个方法  distplot(age)  画出age的树状图"></a>客串seaborn中的一个方法  distplot(age)  画出age的树状图</h3><pre class=" language-python"><code class="language-python">sns<span class="token punctuation">.</span>distplot<span class="token punctuation">(</span>age<span class="token punctuation">)</span></code></pre><p><img src="https://img-blog.csdnimg.cn/20190915112502222.PNG?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mzg5NTQ4Mg==,size_16,color_FFFFFF,t_70" alt="在这里插入图片描述"></p><h3 id="describe-简要显示数据的数字特征"><a href="#describe-简要显示数据的数字特征" class="headerlink" title="describe()  简要显示数据的数字特征"></a>describe()  简要显示数据的数字特征</h3><pre class=" language-python"><code class="language-python">allData<span class="token punctuation">[</span><span class="token string">'Fare'</span><span class="token punctuation">]</span><span class="token punctuation">.</span>describe<span class="token punctuation">(</span><span class="token punctuation">)</span></code></pre><p><img src="https://img-blog.csdnimg.cn/20190915113352696.PNG?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mzg5NTQ4Mg==,size_16,color_FFFFFF,t_70" alt="在这里插入图片描述"></p><pre><code>### ~corr() 计算相关系数</code></pre><ul><li>method：可选{‘pearson’, ‘kendall’, ‘spearman’}<ul><li>pearson: standard correlation coefficient</li><li>kendall: Kendall Tau correlation coefficient</li><li>spearman: Spearman rank correlation</li></ul></li><li>min_periods： Minimum number of observations required per pair of columns to have a valid result. Currently only available for pearson and spearman correlation </li></ul><pre class=" language-python"><code class="language-python"><span class="token comment" spellcheck="true"># 计算标准相关系数</span>corr_matrix <span class="token operator">=</span> housing<span class="token punctuation">.</span>corr<span class="token punctuation">(</span><span class="token punctuation">)</span>corr_matrix<span class="token punctuation">[</span><span class="token string">"median_house_value"</span><span class="token punctuation">]</span><span class="token punctuation">.</span>sort_values<span class="token punctuation">(</span>ascending<span class="token operator">=</span><span class="token boolean">False</span><span class="token punctuation">)</span><span class="token comment" spellcheck="true">#输出：</span><span class="token comment" spellcheck="true"># median_house_value    1.000000</span><span class="token comment" spellcheck="true"># median_income         0.687160</span><span class="token comment" spellcheck="true"># total_rooms           0.135097</span><span class="token comment" spellcheck="true"># housing_median_age    0.114110</span><span class="token comment" spellcheck="true"># households            0.064506</span><span class="token comment" spellcheck="true"># total_bedrooms        0.047689</span><span class="token comment" spellcheck="true"># population           -0.026920</span><span class="token comment" spellcheck="true"># longitude            -0.047432</span><span class="token comment" spellcheck="true"># latitude             -0.142724</span><span class="token comment" spellcheck="true"># Name: median_house_value, dtype: float64</span></code></pre>]]></content>
      
      
      
        <tags>
            
            <tag> python </tag>
            
            <tag> Machine Learning </tag>
            
        </tags>
      
    </entry>
    
    
    
    <entry>
      <title>python基础</title>
      <link href="/2020/05/24/python-ji-chu/"/>
      <url>/2020/05/24/python-ji-chu/</url>
      
        <content type="html"><![CDATA[<h1 id="列表"><a href="#列表" class="headerlink" title="列表"></a>列表</h1><p>[TOC]</p><h2 id="列表是什么？"><a href="#列表是什么？" class="headerlink" title="列表是什么？"></a>列表是什么？</h2><p><strong>列表由一系列特定顺序排列的元素组成的。在python中用 [] 来表示列表，并用 , 来分隔其中的元素。</strong></p><pre class=" language-python"><code class="language-python">bicycles <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token string">'trek'</span><span class="token punctuation">,</span> <span class="token string">'cannondale'</span><span class="token punctuation">,</span> <span class="token string">'specialized'</span><span class="token punctuation">]</span><span class="token keyword">print</span><span class="token punctuation">(</span>bicycles<span class="token punctuation">)</span></code></pre><h3 id="访问列表元素"><a href="#访问列表元素" class="headerlink" title="访问列表元素"></a>访问列表元素</h3><p>访问bicycles中的第一个元素</p><p><code>print(bicycles[0])</code></p><p>可以使用title()方法让元素的格式更整洁</p><p><code>print(bicycles[0].title())</code></p><p><strong>注意：在python中，第一个元素的索引为0，而不是1</strong></p><h3 id="使用列表中的各个值"><a href="#使用列表中的各个值" class="headerlink" title="使用列表中的各个值"></a>使用列表中的各个值</h3><p>可以像其他变量一样使用列表中的各个值。例如：</p><pre class=" language-python"><code class="language-python">message <span class="token operator">=</span> <span class="token string">"My first bicycle was a "</span> <span class="token operator">+</span> bicycles<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">.</span>title<span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token string">"."</span><span class="token keyword">print</span><span class="token punctuation">(</span>message<span class="token punctuation">)</span><span class="token comment" spellcheck="true">### My first bicycle was a Trek.</span></code></pre><h3 id="修改、添加和删除元素"><a href="#修改、添加和删除元素" class="headerlink" title="修改、添加和删除元素"></a>修改、添加和删除元素</h3><p>在python中创建的大多数列表都是动态的，这意味着可以随意地对列表进行修改、删除和添加。</p><p>例如：</p><ol><li><p>修改元素的值</p><pre class=" language-python"><code class="language-python"> bicycles <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token string">'trek'</span><span class="token punctuation">,</span> <span class="token string">'cannondale'</span><span class="token punctuation">,</span> <span class="token string">'specialized'</span><span class="token punctuation">]</span> <span class="token keyword">print</span><span class="token punctuation">(</span>bicycles<span class="token punctuation">)</span> bicycles<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token string">'trak'</span> <span class="token keyword">print</span><span class="token punctuation">(</span>bicycles<span class="token punctuation">)</span> <span class="token comment" spellcheck="true">### ['trek', 'cannondale', 'specialized']</span> <span class="token comment" spellcheck="true">### ['trak', 'cannondale', 'specialized']</span></code></pre></li><li><p>添加元素</p><ol><li><p>在列表的末尾添加元素</p><p><strong>使用append()方法</strong></p><pre class=" language-python"><code class="language-python">bicycles <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token string">'trek'</span><span class="token punctuation">,</span> <span class="token string">'cannondale'</span><span class="token punctuation">,</span> <span class="token string">'specialized'</span><span class="token punctuation">]</span><span class="token keyword">print</span><span class="token punctuation">(</span>bicycles<span class="token punctuation">)</span>bicycles<span class="token punctuation">.</span>append<span class="token punctuation">(</span><span class="token string">'ducati'</span><span class="token punctuation">)</span><span class="token keyword">print</span><span class="token punctuation">(</span>bicycles<span class="token punctuation">)</span><span class="token comment" spellcheck="true">### ['trek', 'cannondale', 'specialized']</span><span class="token comment" spellcheck="true">### ['trek', 'cannondale', 'specialized', 'ducati']</span></code></pre></li><li><p>在列表中插入元素</p><p><strong>使用insert()方法</strong></p><pre class=" language-python"><code class="language-python">bicycles <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token string">'trek'</span><span class="token punctuation">,</span> <span class="token string">'cannondale'</span><span class="token punctuation">,</span> <span class="token string">'specialized'</span><span class="token punctuation">]</span><span class="token keyword">print</span><span class="token punctuation">(</span>bicycles<span class="token punctuation">)</span>bicycles<span class="token punctuation">.</span>insert<span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">,</span> <span class="token string">'ducati'</span><span class="token punctuation">)</span><span class="token keyword">print</span><span class="token punctuation">(</span>bicycles<span class="token punctuation">)</span></code></pre></li></ol></li></ol><pre><code>    ### [&#39;trek&#39;, &#39;cannondale&#39;, &#39;specialized&#39;]    ### [&#39;ducati&#39;, &#39;trek&#39;, &#39;cannondale&#39;, &#39;specialized&#39;]    ```</code></pre><ol start="3"><li><p>删除元素</p><ol><li><p>如果要知道删除元素的位置，可以使用del语句删除元素</p><pre class=" language-python"><code class="language-python">bicycles <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token string">'trek'</span><span class="token punctuation">,</span> <span class="token string">'cannondale'</span><span class="token punctuation">,</span> <span class="token string">'specialized'</span><span class="token punctuation">]</span><span class="token keyword">print</span><span class="token punctuation">(</span>bicycles<span class="token punctuation">)</span><span class="token keyword">del</span> bicycles<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token keyword">print</span><span class="token punctuation">(</span>bicycles<span class="token punctuation">)</span><span class="token comment" spellcheck="true">### ['trek', 'cannondale', 'specialized']</span><span class="token comment" spellcheck="true">### ['cannondale', 'specialized']</span></code></pre><ol start="2"><li><p>使用pop方法删除元素</p><p>有时候，你需要将元素从列表中删除，并接着使用它的值。</p><pre class=" language-python"><code class="language-python">bicycles <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token string">'trek'</span><span class="token punctuation">,</span> <span class="token string">'cannondale'</span><span class="token punctuation">,</span> <span class="token string">'specialized'</span><span class="token punctuation">]</span><span class="token keyword">print</span><span class="token punctuation">(</span>bicycles<span class="token punctuation">)</span>popped_bicycles <span class="token operator">=</span> bicycles<span class="token punctuation">.</span>pop<span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token keyword">print</span><span class="token punctuation">(</span>popped_bicycles<span class="token punctuation">)</span><span class="token comment" spellcheck="true">### ['trek', 'cannondale', 'specialized']</span><span class="token comment" spellcheck="true">### specialized</span></code></pre><p>实际上，可以使用pop()来删除列表中的任何位置的元素，只需要在括号中指定要删除的元素的索引即可。</p></li></ol></li></ol></li></ol><h1 id="组织列表"><a href="#组织列表" class="headerlink" title="组织列表"></a>组织列表</h1><h2 id="使用sort-方法对列表进行排序"><a href="#使用sort-方法对列表进行排序" class="headerlink" title="使用sort()方法对列表进行排序"></a>使用sort()方法对列表进行排序</h2><p>在创建的列表中，元素的排列顺序通常是无法预测的，所以可以用sort()方法进行排序。</p><pre class=" language-python"><code class="language-python">bicycles <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token string">'trek'</span><span class="token punctuation">,</span> <span class="token string">'cannondale'</span><span class="token punctuation">,</span> <span class="token string">'specialized'</span><span class="token punctuation">]</span><span class="token keyword">print</span><span class="token punctuation">(</span>bicycles<span class="token punctuation">)</span>bicycles<span class="token punctuation">.</span>sort<span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token keyword">print</span><span class="token punctuation">(</span>bicycles<span class="token punctuation">)</span><span class="token comment" spellcheck="true">### ['trek', 'cannondale', 'specialized']</span><span class="token comment" spellcheck="true">### ['cannondale', 'specialized', 'trek']</span></code></pre><h2 id="使用sorted-进行临时排序"><a href="#使用sorted-进行临时排序" class="headerlink" title="使用sorted()进行临时排序"></a>使用sorted()进行临时排序</h2><p>要保留元素原来的排列顺序，同时以特定的顺序将他们呈现出来，可以使用函数sorted()。</p><pre class=" language-python"><code class="language-python">bicycles <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token string">'trek'</span><span class="token punctuation">,</span> <span class="token string">'cannondale'</span><span class="token punctuation">,</span> <span class="token string">'specialized'</span><span class="token punctuation">]</span><span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">"Here is the original list:"</span><span class="token punctuation">)</span><span class="token keyword">print</span><span class="token punctuation">(</span>bicycles<span class="token punctuation">)</span><span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">"\nHere is the sorted list:"</span><span class="token punctuation">)</span><span class="token keyword">print</span><span class="token punctuation">(</span>sorted<span class="token punctuation">(</span>bicycles<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">"\nHere is the original list again:"</span><span class="token punctuation">)</span><span class="token keyword">print</span><span class="token punctuation">(</span>bicycles<span class="token punctuation">)</span><span class="token comment" spellcheck="true">##########</span><span class="token comment" spellcheck="true">## Here is the original list:</span><span class="token comment" spellcheck="true">## ['trek', 'cannondale', 'specialized']</span><span class="token comment" spellcheck="true">## Here is the sorted list:</span><span class="token comment" spellcheck="true">## ['cannondale', 'specialized', 'trek']</span><span class="token comment" spellcheck="true">## Here is the original list again:</span><span class="token comment" spellcheck="true">## ['trek', 'cannondale', 'specialized']</span></code></pre><h1 id="遍历整个列表"><a href="#遍历整个列表" class="headerlink" title="遍历整个列表"></a>遍历整个列表</h1><pre class=" language-python"><code class="language-python">bicycles <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token string">'trek'</span><span class="token punctuation">,</span> <span class="token string">'cannondale'</span><span class="token punctuation">,</span> <span class="token string">'specialized'</span><span class="token punctuation">]</span><span class="token keyword">for</span> bicycle <span class="token keyword">in</span> bicycles<span class="token punctuation">:</span>    <span class="token keyword">print</span><span class="token punctuation">(</span>bicycle<span class="token punctuation">)</span><span class="token comment" spellcheck="true">##  trek</span><span class="token comment" spellcheck="true">##  cannondale</span><span class="token comment" spellcheck="true">##  specialized</span></code></pre><p>上面这段代码，我们定义了一个for循环，这行代码让Python从列表bicycles中取出一个名字，并将其存储在bicycle中。然后将其打印出来。输出其中的所有的名字。</p><h1 id="创建数值列表"><a href="#创建数值列表" class="headerlink" title="创建数值列表"></a>创建数值列表</h1><h2 id="使用函数range"><a href="#使用函数range" class="headerlink" title="使用函数range()"></a>使用函数range()</h2><pre class=" language-python"><code class="language-python"><span class="token keyword">for</span> value <span class="token keyword">in</span> range<span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">)</span><span class="token punctuation">:</span>    <span class="token keyword">print</span><span class="token punctuation">(</span>value<span class="token punctuation">)</span><span class="token comment" spellcheck="true">## 1</span><span class="token comment" spellcheck="true">## 2</span><span class="token comment" spellcheck="true">## 3</span><span class="token comment" spellcheck="true">## 4</span></code></pre><p>这个示例打印了1—4，这里不包含5.</p><pre class=" language-python"><code class="language-python">numbers <span class="token operator">=</span> list<span class="token punctuation">(</span>range<span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">11</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token keyword">print</span><span class="token punctuation">(</span>numbers<span class="token punctuation">)</span><span class="token comment" spellcheck="true">## [2, 4, 6, 8, 10]</span></code></pre><p>这个示例表示创建列表，列表从2开始，然后不断加2，直到达到或超过最终值，因此最后一个输出结果为10.</p><h1 id="切片"><a href="#切片" class="headerlink" title="切片"></a>切片</h1><p>要创建切片，可以指定要使用的第一个元素和最后一个元素的索引。例如：要输出列表的前三个元素，可指定索引0:3.</p><pre class=" language-python"><code class="language-python">bicycles <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token string">'trek'</span><span class="token punctuation">,</span> <span class="token string">'cannondale'</span><span class="token punctuation">,</span> <span class="token string">'specialized'</span><span class="token punctuation">,</span> <span class="token string">'qin'</span><span class="token punctuation">]</span><span class="token keyword">for</span> bicycle <span class="token keyword">in</span> bicycles<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">:</span><span class="token number">3</span><span class="token punctuation">]</span><span class="token punctuation">:</span>    <span class="token keyword">print</span><span class="token punctuation">(</span>bicycle<span class="token punctuation">)</span><span class="token comment" spellcheck="true">## trek</span><span class="token comment" spellcheck="true">## cannondale</span><span class="token comment" spellcheck="true">## specialized</span></code></pre><p>上面的例子中使用for循环遍历了bicycles列表中的前三个元素，切片可以指定列表中的任意位置。</p><h1 id="元组"><a href="#元组" class="headerlink" title="元组"></a>元组</h1><p>列表非常适用于存储在程序运行期间可能变化的数据集。列表是可以修改的，这对处理网站的用户列表至关重要。然而，有时候需要创建一系列不可修改的元素，元组可以实现这种操作。</p><p><strong>元组的定义方法是圆括号 ()</strong></p><pre class=" language-python"><code class="language-python">dimensions <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token number">200</span><span class="token punctuation">,</span> <span class="token number">50</span><span class="token punctuation">)</span><span class="token keyword">print</span><span class="token punctuation">(</span>dimensions<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token keyword">print</span><span class="token punctuation">(</span>dimensions<span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token comment" spellcheck="true">## 200</span><span class="token comment" spellcheck="true">## 50</span></code></pre><p>元组的值不可修改</p><p><code>dimensions[0] = 250</code></p><p>这句话会报错。</p><pre class=" language-python"><code class="language-python">Traceback <span class="token punctuation">(</span>most recent call last<span class="token punctuation">)</span><span class="token punctuation">:</span>  File <span class="token string">"D:/Program Files (x86)/PychramProjects/python/python_space.py"</span><span class="token punctuation">,</span> line <span class="token number">48</span><span class="token punctuation">,</span> <span class="token keyword">in</span> <span class="token operator">&lt;</span>module<span class="token operator">></span>    dimensions<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">250</span>TypeError<span class="token punctuation">:</span> <span class="token string">'tuple'</span> object does <span class="token operator">not</span> support item assignment</code></pre><p><strong>虽然不能修改元组的元素的值，但是可以给存储的元组的变量赋值。因此，如果要修改前诉矩阵的尺寸，可以重新定义整个元组</strong></p><pre class=" language-python"><code class="language-python">dimensions <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token number">200</span><span class="token punctuation">,</span> <span class="token number">50</span><span class="token punctuation">)</span><span class="token keyword">print</span><span class="token punctuation">(</span>dimensions<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token keyword">print</span><span class="token punctuation">(</span>dimensions<span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">)</span>dimensions <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token number">400</span><span class="token punctuation">,</span> <span class="token number">200</span><span class="token punctuation">)</span><span class="token keyword">print</span><span class="token punctuation">(</span>dimensions<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token keyword">print</span><span class="token punctuation">(</span>dimensions<span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token comment" spellcheck="true">## 200</span><span class="token comment" spellcheck="true">## 50</span><span class="token comment" spellcheck="true">## 400</span><span class="token comment" spellcheck="true">## 200</span></code></pre><h1 id="字典（与-Json类似）"><a href="#字典（与-Json类似）" class="headerlink" title="字典（与 Json类似）"></a>字典（与 Json类似）</h1><p>在python中，字典是一系列键—值对。每个键都与一个值相对应，可以使用键来访问值。和C++中的map很相似。下面是一个简单的字典。</p><pre class=" language-python"><code class="language-python"><span class="token comment" spellcheck="true"># 字典的练习</span>alien_0 <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token string">'color'</span><span class="token punctuation">:</span> <span class="token string">'green'</span><span class="token punctuation">,</span> <span class="token string">'points'</span><span class="token punctuation">:</span> <span class="token string">'5'</span><span class="token punctuation">}</span><span class="token keyword">print</span><span class="token punctuation">(</span>alien_0<span class="token punctuation">[</span><span class="token string">'color'</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token keyword">print</span><span class="token punctuation">(</span>alien_0<span class="token punctuation">[</span><span class="token string">'points'</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token comment" spellcheck="true">## green</span><span class="token comment" spellcheck="true">## 5</span></code></pre><p>同时，也可以在已经建好的字典里面添加键值对。例如：</p><pre class=" language-python"><code class="language-python">alien_0 <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token string">'color'</span><span class="token punctuation">:</span> <span class="token string">'green'</span><span class="token punctuation">,</span> <span class="token string">'points'</span><span class="token punctuation">:</span> <span class="token string">'5'</span><span class="token punctuation">}</span><span class="token keyword">print</span><span class="token punctuation">(</span>alien_0<span class="token punctuation">)</span>alien_0<span class="token punctuation">[</span><span class="token string">'x_position'</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">0</span>alien_0<span class="token punctuation">[</span><span class="token string">'y_position'</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">25</span><span class="token keyword">print</span><span class="token punctuation">(</span>alien_0<span class="token punctuation">)</span><span class="token comment" spellcheck="true">## {'color': 'green', 'points': '5'}</span><span class="token comment" spellcheck="true">## {'color': 'green', 'points': '5', 'x_position': 0, 'y_position': 25}</span></code></pre><p><strong>字典中的值是可以修改的。</strong></p><h3 id="使用-del-函数删除键值对"><a href="#使用-del-函数删除键值对" class="headerlink" title="使用 del 函数删除键值对"></a>使用 del 函数删除键值对</h3><pre class=" language-python"><code class="language-python"><span class="token keyword">del</span> alien_0<span class="token punctuation">[</span><span class="token string">'points'</span><span class="token punctuation">]</span></code></pre>]]></content>
      
      
      
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            <tag> python </tag>
            
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    <entry>
      <title>Hello World</title>
      <link href="/2020/05/24/hello-world/"/>
      <url>/2020/05/24/hello-world/</url>
      
        <content type="html"><![CDATA[<p>Welcome to <a href="https://hexo.io/" target="_blank" rel="noopener">Hexo</a>! This is your very first post. Check <a href="https://hexo.io/docs/" target="_blank" rel="noopener">documentation</a> for more info. If you get any problems when using Hexo, you can find the answer in <a href="https://hexo.io/docs/troubleshooting.html" target="_blank" rel="noopener">troubleshooting</a> or you can ask me on <a href="https://github.com/hexojs/hexo/issues" target="_blank" rel="noopener">GitHub</a>.</p><h2 id="Quick-Start"><a href="#Quick-Start" class="headerlink" title="Quick Start"></a>Quick Start</h2><h3 id="Create-a-new-post"><a href="#Create-a-new-post" class="headerlink" title="Create a new post"></a>Create a new post</h3><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ hexo new <span class="string">"My New Post"</span></span><br></pre></td></tr></table></figure><p>More info: <a href="https://hexo.io/docs/writing.html" target="_blank" rel="noopener">Writing</a></p><h3 id="Run-server"><a href="#Run-server" class="headerlink" title="Run server"></a>Run server</h3><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ hexo server</span><br></pre></td></tr></table></figure><p>More info: <a href="https://hexo.io/docs/server.html" target="_blank" rel="noopener">Server</a></p><h3 id="Generate-static-files"><a href="#Generate-static-files" class="headerlink" title="Generate static files"></a>Generate static files</h3><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ hexo generate</span><br></pre></td></tr></table></figure><p>More info: <a href="https://hexo.io/docs/generating.html" target="_blank" rel="noopener">Generating</a></p><h3 id="Deploy-to-remote-sites"><a href="#Deploy-to-remote-sites" class="headerlink" title="Deploy to remote sites"></a>Deploy to remote sites</h3><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ hexo deploy</span><br></pre></td></tr></table></figure><p>More info: <a href="https://hexo.io/docs/one-command-deployment.html" target="_blank" rel="noopener">Deployment</a></p>]]></content>
      
      
      
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