How to define static constants in a Java enum?

Question

Is there any way to define static final variables (effectively constants) in a Java enum declaration?

What I want is to define in one place the string literal value for the BAR(1...n) values:

@RequiredArgsConstructor public enum MyEnum {     BAR1(BAR_VALUE),     FOO("Foo"),     BAR2(BAR_VALUE),     ...,     BARn(BAR_VALUE);      private static final String BAR_VALUE = "Bar";      @Getter     private final String value; } 

I got the following error message for the code above: Cannot reference a field before it is defined.

Answer 1

As IntelliJ IDEA suggest when extracting constant - make static nested class. This approach works:

@RequiredArgsConstructor public enum MyEnum {     BAR1(Constants.BAR_VALUE),     FOO("Foo"),     BAR2(Constants.BAR_VALUE),     ...,     BARn(Constants.BAR_VALUE);        @Getter     private final String value;      private static class Constants {         public static final String BAR_VALUE = "BAR";     } }