Well, you're actually asking this question in the
SCJA forum. You'd probably want to look at the SCJP forum for answers about SCJP.
Search the existing posts and you'll find answers to your questions. Even look at the JavaRanch SCJP faq. That will help you to 'know what you don't know' and will help you ask more focussed questions. With a more focussed question, people will be better able to answer your questions!
If you are new to Java, you just might want to attempt the SCJA certification first.
Good luck on your quest.
-Cameron McKenzie