How can I set the SHA digest size in java.security.MessageDigest?

I am kinda playing with the SHA-1 algorithm. I want to find out differences and variations in the results if I change few values in the SHA-1 algorithm for a college report. I have found a piece of java code to generate hash of a text. Its done by importing

java.security.MessageDigest

class. However, I want to change the h0-4 values and edit them but I don't know where can I find them? I had a look inside the MessageDigest class but couldn't find it there. Please help me out!

Thanx in advance.