As a Scala developer I'm obviously biased, but I would add "try out scala" to this list.
Why? Because learning new programming paradigms is beneficial whether you stick with them or not. And Scala is easier for a Java developer to start with than Lisp or Haskell or Z or anything so foreign.
It is simple to get into because you can start basically like "java without semicolons", and IntelliJ community edition has excellent Scala support.