[predakanga]

You don't even need to patch any files - you can patch classes at runtime using a "-javaagent" library.

There are plenty of libraries out there to facilitate this such as Javassist or Apache BCEL, and lots of legitimate uses (AOP, instrumentation, etc).

[junon]

It'd be weird to have access to the command line but not to the jars themselves, I think. Creating a jar is simple if you have a zip program.