Tom,
Based on the posts that I have read here at the Ranch, I think it is safe to say that a lot of people don't have any professional experience with Java when they take the SCJP exam. A lot of people are trying to use the certification to get their first job.
The SCJP certification is really just an indication that you understand the language and understand the basics of OO programming--inheritance, encapsulation and
polymorphism. That can all be learned without professional experience.
The material that you learn by reading a typical Java fundamentals textbook such as Core Java or any of the others is more than you need for the certification. If you have recently read such a book and have most of the information fresh in your memory, then your next step is to just focus your studies of the subset of information that is relavant to the exam. You could do that by reading a SCJP study guide, but you will find that most of the content is a review of what you have recently learned. A second approach would be to just try some mock exams to see where you need a little review. If you try my mock exams, then please keep in mind that my exams are more difficult than the real exam. Your score on the real exam will probably be higher than your score on my exam. Since the passing score on the real exam is only about 51%, you can get a very low score on my exam and still pass the real exam.
My book just became available earlier this week. For that reason, it can only be found on the retail web site for the company that prints it. It won't be available on Amazon until some time in August. Please click on the link in my signature.