I would suggest to leave out differences between JDK 6 and 7, go pick SCJP 6.0 book and start studying. Meanwhile, when OCJP 7.0 book becomes available, you'll be in good shape to go for exam (at that time, all you'll have to cover is differences between JDK 6 and 7 only - which shouldn't take more than a couple of weeks).
Joseph Arnold wrote:Current version is OCJP 6. Get Kathy Sierra & Bates SCJP book to guide you in your preparation.
Larsen Raja wrote:1. If you plan to get certified for Java 6, you should be taking up 1Z0-851.
2. SCJP by Kathy Siera & Bert Bates is the best book
3. You can take free mock ups in javachamp.com. Apart from this commercial simulators are available from enthuware, examlabs and a lot more.
4. Basically SCJP book by K&B should be okay, additionally may use Question bank by K&B for practice.