How to add common methods for a few Java enums? (abstract class ancestor?)

Question

I have a few Java enums as such

public enum Aggregation
{
    MORTGAGE( \"Mortgage\" ),
    POOLS( \"Pools\" ),
    PORTFOLIO( \"Portfolio\" );

    private         


        

Answer 1

Favor composition over inheritance and programming for the sake of interfaces. Since Enums are classes (not regular, but still - classes) you can create some field containing shared logic, let the enum implement you interface and delegate implementation to this field.

Relevant code snippets:

Shared interface

public interface MyInterface {

    void someMethod();

}

Logic implementation

public class MyInterfaceImpl implements MyInterface {

    public void someMethod() {
        System.out.println("Do smth...");
    }

}

First enum

public enum EnumA implements MyInterface {
    ;

    private MyInterface impl = new MyInterfaceImpl();

    public void someMethod() {
        impl.someMethod();
    }

}

Second enum

public enum EnumB implements MyInterface {
    ;

    private MyInterface impl = new MyInterfaceImpl();

    public void someMethod() {
        impl.someMethod();
    }

}

Please do note that EnumA and EnumB are not really code duplication, since that is plain delegation (valid, in my opinion). Also please note that everything is nicely glued together by using interface.