What is the meaning of defining enums and fields inside annotation declarations?

[Mário Guimarães]

 Hello,

It seems it is possible to declare fields and enums inside the declaration
of an annotation in Java. For example, javac compiles this:

 @interface ClassPreamble {
   public enum AnEnum {
        Value;
   }
   String aField = "";

   String author();
   String date();
   String currentRevision() default "";
   String lastModified() default "N/A";
   String lastModifiedBy() default "N/A";
   // Note use of array
   String[] reviewers();}

What is the meaning / usefulness of defining enums and fields inside
annotation declarations?

Thanks

Mário
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