I came from a mainframe background (18 years) and just started with
Java last April.
Here are my prep suggestions:
1) You can not write too many examples of code.
Make examples of what does and doesn't work (both are equally important) for everything. I created a folder for each objective and constantly went back and added to them.
2) Write your own study guide, in your own words, with your own diagrams.
3) I depended on Ivor Horton's Beginning Java 2 SDK 1.4 Edition book and thought it was great preparation. My other book was 'Thinking in Java'
4) Read and become familiar with the JSL and API documentation
5) The internet is loaded with material, especially JavaRanch! Every issue I came up with had already been asked and answered here. Also, make sure to take, and retake, the mock exams.
6) finally, know the given objectives and you'll be fine. I spent way too much study time on Collection methods, order of variable initialization, local inner classes, ambiguous references and the like.
Good Luck!