What Java implementations, other than ports of the Sun JDK, are available for Linux?
The GNU Compiler for Java (GCJ) is a native-language compiler for Java, and part of the GNU compiler suite. Together with the GNU Classpath project, GCJ provides a development and runtime environment for building native applications from Java source.
TowerJ is a commercial deployment environment for Java server-side applications. Using ahead-of-time compilation and a proprietary runtime engine, TowerJ boasts the best runtime performance available on an i386 platform.