Possible Duplicate:
Is it worth to obfuscate java web application?
I have writen an applet. I don't want other people to decompile it using easily availabe decompilers. I have taken lots of pains to implemented the code. Can anyone suggest how I can protect my applet from geting decompiled?
You could always try to use an obfuscator like Proguard or yGuard, but resistance if almost always futile.
With a proper tool, like Java Decompiler, and enough time and expertise, your code will be broken.
Consider whether you're wasting your time with obfuscation. It costs time and money and usually doesn't protect the code against anyone really determined to decompile it.
Instead make your applet better and better, because that would mean someone would have to decompile it again and again and eventually, they will just use your code because it's easier ... as long as it is easier. If you applet sucks, someone else will come up with a better one and you will loose, no matter how you "protect" your code.
Read Getting Real and Rework on how to make your applet better.