ProGuard

ProGuard is a Java class file shrinker, optimizer, obfuscator, and preverifier. The shrinking step detects and removes unused classes, fields, methods, and attributes. The optimization step analyzes and optimizes the bytecode of the methods. The obfuscation step renames the remaining classes, fields, and methods using short meaningless names. These first steps make the code base smaller, more efficient, and harder to reverse-engineer. The final preverification step adds preverification information to the classes, which is required for Java Micro Edition or which improves the start-up time for Java 6.