Hi Himanshu!
There are complete VNC viewers (and probably servers too) written in Java,
RealVNC for example - but I'm guessing that your project is to write the whole implementation of the protocol, not just using a library which does all of it... So basically, I don't think that there's a library that will do part of the work for you. Guess you'll have to do all of it yourself.
Mind you, I've never tried implementing that or any similar protocol in Java, so I may be missing something.
Greetings,
Nepomuk