How to use @inherited annotation in Java?

Question

I am not getting the @Inherited annotation in Java. If it automatically inherits the methods for you then if I need to implement the method in my own way then what about that ?

How does will it come to know my way of implementation ?

Plus it is said if I do not want to use this and do it rather in an old fashioned Java way I have to implement the the equals(), toString(), and the hashCode() methods of the Object class and also the annotation type method of the java.lang.annotation.Annotation class.

Why is that?

I have never implemented those even when I did not know about the @Inherited annotation and the programs used to work fine also .

Please somebody explain me from the scratch about this.

Answer 1

Just that there is no misunderstanding: You do ask about java.lang.annotation.Inherited. This is a annotation for annotations.It means that subclasses of annotated classes are considered having the same annotation as their superclass.

Example

Consider the following 2 Annotations:

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

and

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

If three classes are annotated like this:

@UninheritedAnnotationType class A {      }  @InheritedAnnotationType class B extends A {      }  class C extends B {      } 

running this code

System.out.println(new A().getClass().getAnnotation(InheritedAnnotationType.class)); System.out.println(new B().getClass().getAnnotation(InheritedAnnotationType.class)); System.out.println(new C().getClass().getAnnotation(InheritedAnnotationType.class)); System.out.println("_________________________________"); System.out.println(new A().getClass().getAnnotation(UninheritedAnnotationType.class)); System.out.println(new B().getClass().getAnnotation(UninheritedAnnotationType.class)); System.out.println(new C().getClass().getAnnotation(UninheritedAnnotationType.class)); 

will print a result similar to this (depending on the packages of the annotation):

null @InheritedAnnotationType() @InheritedAnnotationType() _________________________________ @UninheritedAnnotationType() null null 

As you can see UninheritedAnnotationType is not inherited but C inherits annotation InheritedAnnotationType from B.

I don't know what methods have to do with that.