Does compiling Java to native code protect the source code?

Question

Now, I know that...

Anything can be reverse engineered, given enough time and resources.

However, would compiling your Java code to native code with a tool like GCJ make it more difficult to decompile? I mean, given a few minutes, I can decompile a .jar using JD-GUI, and it is relatively accurate. Most of the "Java to EXE" converters are just .exe launchers for the JVM, and while there are many benefits to the JVM, I have been led to believe that security of the source code is not one of them.

Bottom line: Can you use something like GCJ to compile your Java source (or .class) files to native machine code, and if so, will that protect it from decompiling?

EDIT: Ideally, it would be something more than just obfuscation. The specific project is a commercial game, so what we are looking for is a way to make it more difficult to get to the source code to begin with, not just understand it. Also, I'm not sure that Steam accepts .jars, and we are planning on submitting it to the new Green Light project.

Answer 1

I wouldn't choose that approach just for source-security.

Check out some Obfuscator tools out there like ProGuard

If you want to see what those tools do to your source code, just try read the decompiled Minecraft jar if you have one on hand.

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A downside to using this is, that if your code depends on using reflection, you'll have to configure the tools to ignore those functions/classes/whatever, as those will not be found at runtime otherwise.

Answer 2

Technically, yes. Using something like GCJ will make it harder to decompile, however keep in mind that you are losing some major benefits of using Java if you do this. Namely, you lose the ability to write cross-platform applications.

You could use an obfuscator to make the code harder to decompile AND still keep the benefits of using Java.