java decompile

One last tradeoff stems from the dynamically linked nature of Java programs combined with the close relationship between Java class files and the Java programming language. Because Java programs are dynamically linked, the references from one class file to another are symbolic. In a statically-linked executable, references between classes are direct pointers or offsets. Inside a Java class file, by contrast, a reference to another class spells out the name of the other class in a text string. If the reference is to a field, the field’s name and descriptor (the field’s type) are also specified. If the reference is to a method, the method’s name and descriptor (the method’s return type, number and types of its arguments) are specified. Moreover, not only do Java class files contain symbolic references to the fields and methods of other classes, they also contain symbolic references to their own fields and methods. Java class files also may contain optional debugging information that includes the names and types of local variables. A class file’s symbolic information, and the close relationship between the bytecode instruction set and the Java language, make it quite easy to decompile Java class files back into Java source. This in turn makes it quite easy for your competitors to borrow heavily from your hard work.

While it has always been possible for competitors to decompile a statically- linked binary executable and glean insights into your program, by comparison decompilation is far easier with an intermediate (not yet linked) binary form such as Java class files. Decompilation of statically-linked binary executables is more difficult not only because the symbolic information (the original class, field, method, and local variable names) is missing, but also because statically-linked binaries are usually heavily optimized. The more optimized a statically-linked binary is, the less it corresponds to the original source code. Still, if you have an algorithm buried in your binary executable, and it is worth the trouble to your competitors, they can peer into your binary executable and retrieve that algorithm.

Fortunately, there is a way to combat the easy borrowing of your intellectual property: you can obfuscate your class files. Obfuscation alters your class files by changing the names of classes, fields, methods, and local variables, but without altering the operation of the program. Your program can still be decompiled, but will no longer have the (hopefully) meaningful names you originally gave to all of your classes, fields, methods, and local variables. For large programs, obfuscation can make the code that comes out of the decompiler so cryptic as to require nearly the same effort to steal your work as would be required by a statically-linked executable.

FROM HERE

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