Hi Vinu,
My advise to you is that you try some good mocks first(Marcus is the closest to the real exam).
If you find that you are score well on this exam. Then you can start preparing for
Java Tiger right now. Java Tiger has new features and its exam is going to be a little tougher but more like real life situations.
So, if you have practical experience on java then its going to be very helpful to you.
Java 1.4 exam is more like cramming concepts and appearing for the exam.
You can check you much you know about java 1.4 by giving some good mocks.
Now, it is going to be your decision what you want to do!!!
If you score well on mocks then you will be ready in less than a month for the final exam. But if you are not scoring well, then you have to prepare from scratch.
I would say that if you have to prepare from scratch then why now java 1.5, and its exam will be available from April 2005. So you will have plenty of time in hand.
But if you are in a hurry, you can give java 1.4 .
Best of Luck
Kaps