Creating maven project with sub-modules:-
Step 1: Generate new maven project
mvn archetype:generate
Step 2: Go to project [StringManipulation] directory and create modify-strings module
mvn archetype:generate -DgroupId=com.knoldus.stringmanipulation -DartifactId=modify-strings
Step 3: Go to modify-strings module and create two module [modify-string as parent module]
mvn archetype:generate -DgroupId=com.knoldus.stringmanipulation -DartifactId=string-api
Step 4: Method [1. reverseString() 2. getStringLength() ] created
Step 5: Inside string-impl main class created and both methods called
Step 6 : Mandatory dependencies/plugins added in parent pom.xml