Mates, I do have one problem. While I regard myself as a full-stack engineer (C,C++,Java,JavaScript,PHP,HTML,CSS, etc.) I get bombed at every single interview exclusively with Java questions. I know Java and I can solve problems in it, but in my last two interviews my Java code was not elegant enough and my solution not fast or smooth enough.<p>Can you guys advice me a Java exercise reference that includes nice short problems for Object Oriented Java including advanced data structure stuff. It would be important that it also comes with a solution section such that you can actually compare your solution with a suggested one ...<p>Thanks!