If you are doing the SCJD
assignment, to get a better idea of what the project is, I recommend the "SCJD Exam with J2SE5" book. It is a short book, and direct to the point. I am sure it will help you about any topic you have.
The book explains in details how to use the random access objects to access a file, and implements an example database.
The second tool is this forum. As you could see, your first question was asked quicly.