Is there a java classfile / bytecode editor to edit instructions? [closed]

Answer 1

I have not seen any byte code -> byte code frontends, but plenty backends.

I would suggest that you have a look at the many byte code manipulation libraries like javassist which allow loading byte code, manipulate it, and save it back to disk, and then write a small main that does exactly that.

Answer 2

Find this list of byte code manipulation/code generation libraries helpful?

Answer 3

I use reJ for editing class files directly.

It allows you to edit instructions, methods, constant pool, diff classes, and a split view with a hex editor.

It's ridiculously awesome.

Answer 4

I wrote an open source Java assembler and dissasembler you may find useful.

It lets you disassemble a classfile into human readable assembly, edit it, and then reassemble it into a class. It was originally designed for writing obfuscated crackmes, so there are a lot of obscure features it supports that many other tools don't. If you need any features it doesn't currently support, feel free to contact me and I'll see what I can do.