Java Enum definition

Question

I thought I understood Java generics pretty well, but then I came across the following in java.lang.Enum:

class Enum<E extends Enum<E>>

Could someone explain how to interpret this type parameter? Bonus points for providing other examples of where a similar type parameter could be used.

Answer 1

You are not the only one wondering what that means; see Chaotic Java blog.

“If a class extends this class, it should pass a parameter E. The parameter E’s bounds are for a class which extends this class with the same parameter E”.