JRuby is an quite an exciting Ruby interpreter. While some may shy away from it since it runs on the Java VM, something not well liked by many programmers, JRuby is quite interesting and in many cases faster than MRI, the official Ruby interpreter. But this isn't why it's particularly exciting. It's exciting because you have access to the huge library of Java code out there and can use it directly from your Ruby code, without any visible "glue." So we'll install JRuby on Windows and write a very quick GUI application.