What training projects can you do to pump different sides?

Question

Java

What kind of training projects can be done to pump various sides and skills (the whole java core, java ee)
From the banal, there are online stores, blogs, social networks in mind.
What else can be added to this list in the same vein?

Answer 1

Programming
puzzles The best way I think is the development of real applications. There are ideas - to realize them; if they are not there, copy other applications without knowing their source code.
Simple examples: Calculator; paint; Notebook; PDF editor; Audio editor; Audio player; etc.

Answer 2

What can be pulled into one in Java?