JRuby is an implementation of the Ruby programming language in Java. The common Ruby implementation is in C. So what is so cool another implementation of Ruby in Java?
Well, I did several small applications in Java, and it was my language of choice for some time now. Java is Free, and lots of IDE's are free, like eclipse, and netbeans. Java has millions of free libraries for almost anything. Java can be used on the server with jsp, j2ee and on the client with Swing. So it's an all-in-one language.
So, having a Ruby implementation in Java, you can leverage your Java code, and use the elegance and beauty, and fun of coding in Ruby. You can extend your Java classes using Ruby, and you can automate some of the high level work for your applications using Ruby.
Another GREAT news is that JRuby is now endorsed, and officially supported by Sun. The core JRuby developers are paid by Sun. Way to go Sun!
There are some nice tutorials in the JRuby site. I'll try that out myself and see how far I can go with JRuby.