Researchers at Oxford have built an x86 emulator that runs purely on Java, making it ideal for security researchers who want to analyze and archive viruses, host honeypots and defend themselves against buggy or malicious software without hosing their machines. The JPC also emulates a host of other environments, giving technophiles the ability to play Asteroids and other software that’s sat on shelves for years collecting dust.

http://www.theregister.com/2007/03/23/java_emulator/