Hi Charles...
If you hope to sit scjp exam , I would prefer you to use
scjp study guide for java6 by K&B. That book is the most popular one among scjp test takers. After reading from cover to cover, you will get a deep knowledges of
java theory. There are a lot of self-test questions you can answer in the book. And then
you should practise with some pre-exam kits.I used
Devaka's ExamLab to make my knowledges strong.
And yes,I really met with a easy threading and a lot of Generic/Collection questions, but I don't want to say threading is not emphasized for this exam. The questions may differ for each candidates. So , it would be better for you to prepare for all objectives.
I hope you do well in the exam...
Yewint..