Good to hear you are making progress with java.
I would find a nice java book on the library (or maybe warez), not to read, but to make the the exercises in. This should test a lot of aspects of programming, and usually has the information to cover to it, should you get stuck.
I quite liked "Object-Oriented Design and Patterns, Cay Horstmann", as it works in general OOP concepts, but uses java for implementation.
But there are tons of books out there, just dont go spend to much on them, if you are only gonna make the exercises anyway.