Inheritance in enum

Question

I have given an enum ABC and a class Test and I have to call doSomething but I cannot pass ABC enum as parameter.

enum ABC{
   A,B,C;
 }

Class Test{

  public void doSomething(ABC abc)
  {
    //some work
   }

}

Here I want an enum DEF that should have all member of ABC and it should also have member of enum XYZ (I want an enum DEF that should contain members of two enums(ABC and XYZ)). Example like this.

 enum DEF 
 {
    A,B,C,X,Y,Z,D;
 }

 enum xyz{
     X,Y,Z;
 }

So that I can call doSomething method which takes only ABC enum as parameter. I want to call doSomething() method with DEF.Example

  class Demo{

     public static void main(String[] ags)
     {
         Test test= new Test();
         test.doSomething(DEF.A);
      }

 }

I am fresher. Kindly provide me any help or suggestion.I will be thankful to you.

You can't extend `enum`s. However you can make an interface `MyInterface` with a method `doSomething()`, and then make `ABC` and `XYZ` both implement `MyInterface`. That way you could call `doSomething()` on any of the six `enum` constants. — Paul Boddington, Dec 20 '14 at 16:10

score 9 · Answer 1 · edited May 23 '17 at 11:52

Enums in Java are final, which means you cannot extend and enum (you cannot add more values to existing enum). In you case the ABC and DEF are completely different entities with simple the same names of enum items. This implicates for example that ABC.A != DEF.A.

There are many ways to handle that, however none of them is perfect or simple. You should evaulate what is needed in your specific case.

First way to handle that is to create a common interface, which your enums can extend:

interface MyInterface{

}

enum ABC implements MyInterface{
   A,B,C;
 }

enum DEF implements MyInterface{ 
    A,B,C,X,Y,Z,D;

 }

This way you can use both ABC and DEF in doSomething():

Class Test{

  public void doSomething(MyInterface abc)
  {
    //some work
   }

 }

Other approach is to add generics to your class. This way you can create concrete implementations which will support specified enum:

class GenericTest<E extends Enum<E>>{
    public void doSomething(E enum){
    }
}

class TestWhichAcceptsABC extends GenericTest<ABC>{}

class TestWhichAcceptsDEF extends GenericTest<DEF>{}

Third way is to create multiple methods, one for each enum which need to be handled

Class Test{

   public void doSomething(ABC abc)
   {
    //some work
   }

   public void doSomething(DEF abc)
   {
    //some work
   }

}

See This thread for more ideas how to solve enum inheritance.

score 1 · Answer 2 · answered Dec 20 '14 at 16:29

Even though you have mentioned in same name it doesnt mean same in enum. For Example A in ABC is instance of ABC. But A in DEF is instance of DEF. So its different. You can implement interface in enum.

enum ABC implements X{
    A,B,C;
}

public class Test{

    public void doSomething(X x)
    {

    }
}

You will try this.

Icy Creature · Answer 3 · 2014-12-20T20:32:34.740

-2

You can't extend enums but you can do the next best thing by simulating the behaviour of an enum. You can create a class with static value. Like this.

public class abc extends yxz {
    public static final int A = 1;
    public static final int B = 2;
    public static final int C = 3;
}

edited Dec 20 '14 at 20:32

answered Dec 20 '14 at 16:41

Icy Creature

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Inheritance in enum

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