you have to write native c codes and also u need to undertstand jni.
with pure java  you have no way to produce these low level networking
actions.

> well i m working  on ANTI-Dos attacks. i want to know that how can i
change the IP add  of the outgoing packet  of my machine.

If you're trying to defend against DOS attacks, you'd be looking for a
proxy with governing and tempering controls of sorts, not for ways to
screw around with the make up of packets.