It seems you can get a null pointer exception using enumerations and case statements. Ouch, my first gut instinct is why use a case statement? The enumerations in Java 1.5 support methods. Let polymorphism be your guide.
Of course, I'm surprised the minds at Sun let such mistakes go by. Both auto-boxing and enumerations allow null pointer exceptions that most coders will not catch because typically you don't expect them (because of the expansion of the real code). I think this is going to catch a lot of unsuspecting developers. Java has trained our eyes and minds to where potential null pointer exceptions could lie. Ouch. The rules have now changed.
Again, nulls rears its ugly head to smash down all of that compile type checking non-sense. It all compiles, but will it run? How much do you want to pay for safety that's not guaranteed? I'd rather not fight monsters with blankeys, but with a real sword (unit tests).