Annotation interface in Java

java.lang.annotation.Annotation

The common interface is extended by all annotation types. Note that an interface that manually extends this one does not define an annotation type. Also, note that this interface does not define an annotation type.

The java.lang.reflect.AnnotatedElement interface discusses compatibility concerns when evolving an annotation type from being non-repeatable to being repeatable.

Declaration

public interface Annotation {

    boolean equals(Object obj);

    int hashCode();

    String toString();

    Class<? extends Annotation> annotationType();
}

Methods

1. equals(Object obj)

boolean java.lang.annotation.Annotation.equals(Object obj)

Returns true if the specified object represents an annotation that is logically equivalent to this one.

Parameters: obj the reference object with which to compare.

Returns: true if the specified object represents an annotation that is logically equivalent to this one, otherwise false

2. hashCode()

int java.lang.annotation.Annotation.hashCode()

Returns the hash code of this annotation, as defined below:

The hash code of an annotation is the sum of the hash codes of its members (including those with default values), as defined below:

The hash code of an annotation member is (127 times the hash code of the member-name as computed by String.hashCode()) XOR the hash code of the member value, as defined below:

Returns: the hash code of this annotation

3. toString()

String java.lang.annotation.Annotation.toString()

Returns a string representation of this annotation.

Returns: a string representation of this annotation.

4. annotationType()

Class<? extends Annotation> java.lang.annotation.Annotation.annotationType()

Returns the annotation type of this annotation.

Returns: the annotation type of this annotation.

Some other classes/interfaces of java.lang.annotation

Native: Indicates that a field defining a constant value may be referenced from native code.

Inherited: Indicates that an annotation type is automatically inherited.

IncompleteAnnotationException: Thrown to indicate that a program has attempted to access an element of an annotation type that was added to the annotation type definition after the annotation was compiled (or serialized). 

AnnotationFormatError: Thrown when the annotation parser attempts to read an annotation from a class file and determines that the annotation is malformed.

ElementType: The constants of this enumerated type provide a simple classification of the syntactic locations where annotations may appear in a Java program.

Documented: If the annotation @Documented is present on the declaration of an annotation type A, then any @A annotation on an element is considered part of the element's public contract.

AnnotationTypeMismatchException: Thrown to indicate that a program has attempted to access an element of an annotation whose type has changed after the annotation was compiled.

Annotation: The common interface is extended by all annotation types.

Repeatable: The annotation type is java.lang.annotation.Repeatable is used to indicate that the annotation type whose declaration it(meta-)annotates is repeatable.

Retention: Indicates how long annotations with the annotated type are to be retained. If no Retention annotation is present on an annotation-type declaration, the retention policy defaults to RetentionPolicy.CLASS.

RetentionPolicy: Annotation retention policy. The constants of this enumerated type describe the various policies for retaining annotations.

Target: Indicates the contexts in which an annotation type is applicable.