'Java 2 Exam Cram' is a great book as it directly addresses all the less well known, but frequently argued, parts of Java. I also recommend looking through the

'Java 2 Exam Cram' is a great book as it directly addresses all the less well known, but frequently argued, parts of Java. I also recommend looking through the source code of any frameworks you are using in order to build up your knowledge. It's always helpful to see how other people do things and will periodically give you a confidence boost as well.