Can enums be subclassed to add new elements?

Question

I want to take an existing enum and add more elements to it as follows:

enum A {a,b,c}

enum B extends A {d}

/*B is {a,b,c,d}*/

Is this po

Answer 1

As an aid to understanding why extending an Enum is not reasonable at the language implementation level to consider what would happen if you passed an instance of the extended Enum to a routine that only understands the base Enum. A switch that the compiler promised had all cases covered would in fact not cover those extended Enum values.

This further emphasizes that Java Enum values are not integers such as C's are, for instances: to use a Java Enum as an array index you must explicitly ask for its ordinal() member, to give a java Enum an arbitrary integer value you must add an explicit field for that and reference that named member.

This is not a comment on the OP's desire, just on why Java ain't never going to do it.