Write tests for the project to see if removing a user from a group is working as expected.
Answer Question
Fix a bug when creating a group.
Answer Question
Fix a bug when adding users to a group.
Answer Question
Implement nested groups in the project.
Answer Question
Make the code thread safe and test it.
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 It's peer programming and it's maven user management project .You need to fix all the bugs or implement new feature according to a requirement pdf.

Third Round: Java Concurrency Problem. Factory design pattern.