This link will give you some usefull links for preparation. http://www.javaranch.com/ubb/Forum25/HTML/000126.html
I feel that developer exam is not something like studying one or two books and passing the exam. Its really practical orianted. So far I bought two books for reference. My opinion is not to spend more money for the books. I guess you might be having RHE book. Read the developer's section. I heard that new edition of RHE is better.
Core java Volume I & II.
Lot of free stuffs available in Net. If we make use of it that itself enough.
It's my pleasure to help you. I got l..o..t of help from you when I was preparing for programmers exam.
I don't know how to prioritize. B'cas its all depends on how you are planning to design.
- threads, (syncronized, wait , notify)
- RMI (basics, passing parameters, deploying the class files)
- sockets (yet to study)
- serialization (Basic idea)
- collections (Read about important classes)
- streams (For coding mostly we don't need much. Basic idea)
- javadoc (Try to use most of the functions. Really interesting. . )
- Swing ( JFrame, JTable, JComboBoxes,JButtons,JTextField )
If you want to implements the project in best design you need to study a lot. Its all just my opinion.