There is not too much to hash codes beyound their contracts ( for the SCJP atleast ). You can have a look at what the hash code and equals contract is in the SCJP book series written by Kathy and Bert. I have a link to the java 1.5 version of the book on my signature.
Oh and by the way... "ramya ramya" is not a valid name in this forum. You will need to change it.