Rhino is an open-source implementation of JavaScript written entirely in Java. It is typically embedded into Java applications to provide scripting to end users.
Rhino image courtesy of Paul Houle.
Add reference to http://www.javaworld.com/jw-08-1999/jw-08-howto.html and http://www.javaworld.com/javaworld/jw-09-1999/jw-09-howto.html