How do I edit the actual code of a java .class file?

How do I edit the actual code of a java .class file?

Have a look at decompilers. Theyll transform the java-bytecode back to source code. One example of such a compiler would be JD: http://jd.benow.ca/

After editing the source code you would have to compile the code again and pack it in the respective .jar file.

If your file is an old enough version, you can use jasper to disassemble it into bytecode, edit the bytecode and reassemble it using jasmin. Unfortunately these tools have not been updated in some time.

They do not produce Java code; youll have to learn Java bytecode. But it is more reliable than the so-called decompiler methods.

How do I edit the actual code of a java .class file?

As Java .class files are in byte-code format, you cannot modify them the way you would edit a .java source file. Bytecode is a low level language closer to the machine language rather than Java itself.

If you need to modify the source, one option is to use a decompiler, e.g. JAD (Java Decompiler), to get a source file and then change it and recompile to .class using javac. Make sure you figure out which version of Java language (1.4, 5, 6, 7, 8) has been used for the original jar file.

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