Is there any way we can inject new methods and properties into classes during run-time.
http://nurkiewicz.blogspot.com/2009/09/injecting-methods-at-runtime-to-java.h
So if you were really crazy, you could do something like what they outline here. What you could do is load the .java file, find the correct insertion point, add whatever methods you need to, call the java compiler and reload the class. Good luck debugging that mess though :)
Edit This actually might be of some use...