Jikes is a compiler that translates Java source files as defined in The Java Language Specification into the bytecoded instruction set and binary format defined in The Java Virtual Machine Specification. You may wonder why the world needs another Java compiler, considering that Sun provides javac free with its JDK. Jikes has four advantages that make it a valuable contribution to the Linux and Java communities: open source, strictly Java compatible, high performance, dependency analysis.

GCJ is a portable, optimizing, ahead-of-time compiler for the Java Programming Language. It can compile:

• Java source code directly to native machine code,
• Java source code to Java bytecode (class files),
• and Java bytecode to native machine code.

Compiled applications are linked with the GCJ runtime, libgcj, which provides the core class libraries, a garbage collector, and a bytecode interpreter. libgcj can dynamically load and interpret class files, resulting in mixed compiled/interpreted applications.