Tim points out that if you know your way around the Java libs you are in great shape to use a dynamic programming environment on the JVM.
Tim reckons some people will be mad at him for saying that. I'm not one of them. Bewilderment laced with a tincture of frustration would be my position.
IMO, Tim is absolutely right. As I said in a recent IT World article The Library IS The Programming Language.
Getting up to speed with a programming language syntax and semantics is a matter of days. Getting up to speed with the quintillion libraries that make you productive can take years.
If you know your way around the JDK, have a bunch of third party libs and a bunch of libs you developed yourself then do yourself a favor. Install Jython and watch your productivity jump.
If that does not tickle your fancy, try Ruby or Rhino or SISC or...there are lots to choose from!
BTW, calling all developers with deep knowledge of Java. The Jython world could use your help. Two years ago I would have said "to keep pace with CPython" but today it would be more appropriate to say "to keep pace with IronPython".
I fear, that the Java world is on the verge of snatching defeat from the jaws of victory on the dynamic language front.
I'd hate to see that happen.