jruby implements most of the ruby features.
Support for interacting with and defining java classes from within ruby.
Q: j4 jruby
A: using Ruby for tools and tasks where Java only incurs overhead is a
very compelling for Java developers
Q: How do I use it if i already know how to program and run a ruby program?
A: you should be able to just use your Ruby scripts with JRuby
keep learning 活到老学到老 