Question

I have an enum, let’s call it A:

public enum A
{
    A,
    B
}

I have a function that takes an enum A:

public void functionA(A enumA)
{
    //do something
}

How can I create another enum, possibly call B that I can pass to functionA? Something like this?

public enum B
{
    C
}

functionA(B.C);

I know that you can’t extend an enum, but what other options do I have available? What is the best way to achieve this?

Answer 1

You can’t.

Enum types are final by design.

The reason is that each enum type should have only the elements declared in the enum (as we can use them in a switch statement, for example), and this is not possible if you allow extending the type.

You might do something like this:

public interface MyInterface {
    // add all methods needed here
}

public enum A implements MyInterface {
    A, B;
    // implement the methods of MyInterface
}

public enum B implements MyInterface {
    C;
    // implement the methods of MyInterface
}

Note that it is not possible to do a switch with this interface, then. (Or in general have a switch with an object which could come from more than one enum).