It's difficult to prepare for an exam using a book that covers a different version. This is especially true regarding Java 1.4 and 5.0, because these exams are significantly different.
If you have the book for 5.0, I really think you should consider the 5.0 exam. There is a lot of new material on the 5.0 exam that you will be seeing in the book (and will use in practice), so you may as well get certification credit for knowing it. Also, there is some material on the 1.4 exam that is not covered in the 5.0 exam (for example, bit manipulation and the Math class), so if you're taking the 1.4 exam you will need to cover those topics elsewhere.
The answer of the same exam question can be different, depending on if you're using 1.4 or 5.0. For example, some things do not compile on Java 1.4 but do on Java 5.0. On the exam, the answer "does not compile" would in that case be correct for 1.4, but wrong for 5.0.