Question

Isn’t it impossible to extend a generic type with an undefined type parameter ex:

class Foo extends enum<E>

How do they extend it?

edit: also where is the values() method defined?

Thanks in advance

Answer 1

It is indeed illegal to extend a generic type with an undefined type parameter. However, enums don’t do that. If you’re decompiling some java code and saw a <E> there (And your enum type is not named E), your decompiler isn’t processing generics properly.

An enum implicitly extends Enum<YourEnumType>. That is, implicitly the compiler generates a class YourEnumType extends Enum<YourEnumType>. By passing down its own type, it allows Enum‘s compareTo and valueOf functions to reject values from different types of enums.