ProGuard

ProGuard is a free Java class file shrinker, optimizer, obfuscator, and preverifier. It detects and removes unused classes, fields, methods, and attributes.

It optimizes bytecode and removes unused instructions. It renames the remaining classes, fields, and methods using short meaningless names. Finally, it preverifies the processed code for Java 6 or for Java Micro Edition.

ProGuard's main advantage compared to other Java obfuscators is probably its compact template-based configuration. A few intuitive command line options or a simple configuration file are usually sufficient.

ProGuard is fast - it only takes seconds to process programs and libraries of several megabytes. The results section will present the actual figures for several applications.

ProGuard is a command-line tool with an optional graphical user interface. It also comes with plugins for Ant and for the J2ME Wireless Toolkit.