JAVA ANNOTATIONS: @Inherited

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JAVA ANNOTATIONS: @Inherited

#java #annotations #inherited

· java

Define:

@Inherited annotation indicates that the annotation type can be inherited from the super class.
(This is not true by default.)
This is a annotation for annotations.

It means that subclasses of annotated classes are considered having the same annotation as their superclass.

Snippet:

package vv;

import java.lang.annotation.ElementType;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

public class Test {

	@Inherited
	@Target(ElementType.TYPE)
	@Retention(RetentionPolicy.RUNTIME)
	@interface VVInherited {
	}

	@Target(ElementType.TYPE)
	@Retention(RetentionPolicy.RUNTIME)
	@interface VVNone {
	}

	@VVNone
	class A {
	}

	@VVInherited
	class B extends A {
	}

	class C extends B {
	}

	public static void main(String[] args) {
		out(new Test().new A().getClass().getAnnotation(VVInherited.class));
		out(new Test().new B().getClass().getAnnotation(VVInherited.class));
		out(new Test().new C().getClass().getAnnotation(VVInherited.class));
		out("");
		out(new Test().new A().getClass().getAnnotation(VVNone.class));
		out(new Test().new B().getClass().getAnnotation(VVNone.class));
		out(new Test().new C().getClass().getAnnotation(VVNone.class));
	}

	static void out(Object o) {
		System.out.println(o);
	}
}

Prints:

null
@vv.Test$VVInherited()
@vv.Test$VVInherited()

@vv.Test$VVNone()
null
null

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