Converts Java applications to optimized conventional Windows EXE and DLL files. [Commercial]

The GNU Compiler for Java - compiles Java source or bytecode to native machine code. Most APIs are supported, except the AWT and Swing. [Open Source, GPL]

Java compiler test suite, for testing that Java compilers adhere to the Java Language Specification. [Open Source, GPL]

A command line tools (ja2dol and next generation java2cpp) that translates Java sources into corresponding C++ sources. [Freeware and open source]

Java-to-C Translator: translates Java class files into C source code to allow making directly executable programs. For stand-alone applications, not applets. [Freeware]

Claims to convert Java GUI client-side applications to HTML/JavaScript-based front end with no recoding. [Commercial]