Hi ankit,
Welcome to the JavaRanch!
Maybe it is a good idea to go through the
Reading Materials and the
FAQ first. They will answer a lot of your questions when you want to start with the SCJD.
And the best book for this exam is the "The Sun Certified
Java Developer Exam with J2SE 5, Second Edition" by Andrew Monkhouse (and Andrew is regularly visiting this forum answering the questions you will have and sharing his valuable thoughts).
Kind regards,
Roel