This cannot be stressed enough, mastery of the nuances of a language does not make a person creative or a skilled problem solver which are far more important than if someone uses final, finally or finalize. The last of which I don't believe I have ever used in Java myself.
I personally ask people one simple question and that is what is the thing that you are most proud of that you have created. Then I ask what challenges and difficult problems did you encounter. I do this because it can fill an entire interview with organic conversation, I can see peoples passion instantly, people become less nervous when they don't fell they are being tested and I can steer that conversation into technical discussion to get a feel for their depth of technical understanding.