[devonkim]

Historically, I've used rich enums in Java to be able to use switch statements to reason about a system state and as poor man's type pattern matching. Sometimes the switch is handy for making a state machine clearer, and sometimes it makes it easier to explain the relationships of these states as an ordered list. Another important use of enums is if you're trying to create a rich set of annotations that take parameters, which would force you into dropping a lot of the Java OOP typing available. I can't have a closure or even an anonymous class as an argument to parameterized annotations - and this is definitely by design.

I got bit pretty hard before trying to design an annotation-driven convention for a library I was writing (I had been writing a lot of Python for a while) and realized I'd have to squash a bunch of my carefully arranged classes into an enum. You run into similar problems when marshalling your objects to, say, a Thrift structure definition.