The Java® Language Specification, Java SE 7 Edition, Fourth Edition

8.9. Enums

An enum declaration specifies a new enum type.

EnumDeclaration:    ClassModifiers_opt enum Identifier Interfaces_opt EnumBodyEnumBody:      { EnumConstants_opt ,_opt EnumBodyDeclarations_opt }

Enum types (§8.9) must not be declared abstract; doing so will result in a compile-time error.

An enum type is implicitly final unless it contains at least one enum constant that has a class body.

It is a compile-time error to explicitly declare an enum type to be final.

Nested enum types are implicitly static. It is permissible to explicitly declare a nested enum type to be static.

This implies that it is impossible to define a local (§14.3) enum, or to define an enum in an inner class (§8.1.3).

The direct superclass of an enum type named E is