Are instances of enums static by default?

Question

enum Animals{
    DOG("woof"),
    CAT("Meow"),
    FISH("Burble");

    String sound;

    Animals(String s) {
            sound = s;
    }
}
public class TestEnum{
    static Animals a;
    public static void main(String ab[]){
        System.out.println( a );
        System.out.println( a.DOG.sound + " " + a.FISH.sound);
    }
}

In the above example, why are we able to access instances of the enum (i.e. as a.DOG.sound) when a is null and enum is not declared as static? Are the enum instances static by default?

Answer 1

Enums are implicitly public static final.

You can refer to a.DOG because you may access static members through instance references, even when null: static resolution uses the reference type, not the instance.

I wouldn't; it's misleading: convention favors type (not instance) static references.

See JLS 6.5.6.2 regarding class variable via instances. See JLS 15.11 for why it still works with a null. Nutshell: it's the reference type, not the instance, through which statics are resolved.

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Updated links :/

JSE 6

• JLS 6.5.6.2 regarding class variable access via expression name
• JLS 15.11 regarding static field access via null references

JSE 7

• JLS 6.5.6.2 regarding class variable access via expression name
• JLS 15.11 regarding static field access via null references

JSE 8

• JLS 6.5.6.2 regarding class variable access via expression name
• JLS 15.11 regarding static field access via null references

Answer 2

Yes, enums are effectively static.