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Why can't a Java enum be final?

Asked 2012-03-27T14:29:33.443
34
public interface Proposal  {  
    public static final enum STATUS { 
        NEW ,
        START ,
        CONTINUE ,
        SENTTOCLIENT
    }; 
}

Java does not allow an enum to be final inside an interface, but by default every data member inside an interface is public static final. Can anybody clarify this?

java enums final
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2 Answers

42

Java does not allow you to create a class that extends an enum type. Therefore, enums themselves are always final, so using the final keyword is superfluous.

Of course, in a sense, enums are not final because you can define an anonymous subclass for each field inside of the enum descriptor. But it wouldn't make much sense to use the final keyword to prevent those types of descriptions, because people would have to create these subclasses within the same .java file, and anybody with rights to do that could just as easily remove the final keyword. There's no risk of someone extending your enum in some other package.

answered 2012-03-27T14:30:36.163
8

Two things:

  1. enums are final subclasses of java.lang.Enum
  2. if an enum is a member of a class, it is implicitly static
answered 2012-03-27T14:33:18.433

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