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JODE is a java package containing a decompiler and an optimizer for java. This package is freely available under the GNU GPL. New: The bytecode package and the core decompiler is now under GNU Lesser General Public License, so you can integrate it in your project.

The decompiler reads in class files and produces something similar to the original java file. Of course this can't be perfect: There is no way to produce the comments or the names of local variables (except when compiled with debuging) and there are often more ways to write the same thing. However, JODE does its job quite well, so you should give it a try and start the applet. Jode has support for all constructs of JDK-1.3 including inner and anonymous classes.

The optimizer transforms class files in various ways with can be controlled by a script file. It supports the following operations:

News

Known bugs of the decompiler

Some jdk1.3 synthetic access functions aren't understood. The produced source contains access$xxx functions, but it still compiles.

There may be other bugs, that cause Exceptions or invalid code. If you have such a problems don't hesitate to issue a bug report. Please include the class file if possible.

Limitations

If not all dependent classes can be found, the verifier (which is run before decompilation starts) may exit with a type error. You can decompile it with --verify=off, but take the warning serious, that types may be incorrect. There's sometimes no way to guess the right type, if you don't have access the full class hierarchie.
This is not a bug in the verifier: java will complain the same way, if it is run with bytecode verification turned on. And if you don't have the dependent classes, you can't compile the code again.

There may be situations, where the code doesn't understand complex expressions. In this case many ugly temporary variables are used, but the code should still be compileable. This does especially happen when you compile with `-O' flag and javac has inlined some methods.