This is very convenient now that Java (as of 1.6) has JavaScript/Rhino built in as an implementation of the Scripting API: http://snipplr.com/view/17501/javascript-swing-application/
Execution is as simple as 'jrunscript app.js'.
Execution is as simple as 'jrunscript app.js'.
https://developer.mozilla.org/en/Rhino_documentation
Steve Yegge suggests it's the next big language.