Can Annotation implement interfaces?

Is there any possibility implement interface in annotation? Something like:

public @inter开发者_如何学编程face NotNull implements LevelInterface  {
    ValidationLevel level();
};

No, the compiler says:

Annotation type declaration cannot have explicit superinterfaces

You cannot extend either:

Annotation type declaration cannot have an explicit superclass

No, an annotation can not have super-interfaces^* (although interfaces can extend from an annotation, and classes can implement an annotation, both of which is an awful practice imho)

_{[*] The funny thing is: I can't find any document that explicitly says so, except the java compiler output (neither the Sun Java Tutorial, nor the Java 1.5 Annotations specification)}

No, you can not (as said in my comment). You may use delegation though (as said by AlexR). However, you'll have to use an enum:

public enum LevelEnum implements LevelInterface {
  DEFAULT {
    public ValidationLevel level() {
      // SNIP (your code)
    }
  };
}

public @interface NotNull {
  LevelEnum level() default LevelEnum.DEFAULT;
}

Short answer is No (exactly as Thilo said).

Long answer is if you really wish such functionality you can use delegation: annotation can hold as many as you wish fields that implement as many as you want interfaces. Please see the following example:

public interface LevelInterface {
    public int level();
}

public static LevelInterface foo = new LevelInterface() {
    @Override
    public int level() {
        return 123;
    }

};

 public @interface NotNull {
     LevelInterface level = foo;
 }