dirtyJOE - Java Overall Editor
dirtyJOE - Java Overall Editor is a complex editor and viewer for compiled java binaries (.class files). Current version still have some limitations, but hopefully those will be removed within the next releases.
dirtyJOE is free for non-commercial use.
dirtyJOE is entirely written in C++, no third party libraries were used.
* Viewer for: constant pool, methods, fields, attributes
* Editor for: constant pool, bytecode
You can download it from http://dirty-joe.com