XRuby is the first Ruby to Java compiler which compiles Ruby source code (.rb) to Java bytecode (.class). The parser is implemented in ANTLR, and ASM has been used to emit Java bytecode.
XRuby is able to pass all tests in samples/test.rb and most unit tests in test/ruby/ - a decent test suite that comes with Ruby installation. In most benchmark tests, XRuby runs faster than Ruby 1.8.5.
Platform:MAC OS X License:Apache License 2.0
References:https://code.google.com/p/xruby/