Possible Duplicate:
What types of executables can be decompiled?
It's pretty popular to decompile the Minecraft classes to edit and add your own mods. Is every Java application decompilable? Does it stop at Java applications?
I'm a little concerned about this, but no one else seems to be so maybe I just don't understand. What's stopping people decompiling Microsoft Word and making their own custom changes? Or decompiling World of Warcraft and stealing interesting bits of their code?
Byte code (as java and c# get compiled into) can easily be decompiled. There are ways around it as in obfuscation and other alternatives. C and C++ get compiled into native machine code, and is difficult to "decompile". But someone with the correct skillset could be able to reverse engineer it anyway.
Edit: Note that obfuscation will not make it harder to decompile the byte code - it will be just as easy, but the code will be harder to make any sense of.