Exercises in Java [closed]

in this semester at the university I'm studying java and more generally OOP. My professor gives us an exercise very two weeks, but I solve it in less time and I have no challenging programs to develop during the week. So I ask you: Is there a site where i can download java exercises to import in Eclipse with requirements specified and maybe also JUNIT tests (to check if I did everything right)?

I know it is a very general question (and not a code), but surfing on the net I found only basic execises.

Thanks