Target

AI-generated Key Takeaways

• The @Target meta-annotation specifies the contexts (classes, methods, fields, etc.) where an annotation type can be used.

• If @Target is not present, the annotation can be applied to any declaration except type parameters.

• The value method within @Target returns an array of ElementType enum constants, defining the applicable contexts.

• When present, the compiler enforces the usage restrictions defined by the ElementType constants within the @Target annotation.

public abstract @interface Target implements Annotation

Indicates the contexts in which an annotation type is applicable. The declaration contexts and type contexts in which an annotation type may be applicable are specified in JLS 9.6.4.1, and denoted in source code by enum constants of java.lang.annotation.ElementType.

If an @Target meta-annotation is not present on an annotation type T , then an annotation of type T may be written as a modifier for any declaration except a type parameter declaration.

If an @Target meta-annotation is present, the compiler will enforce the usage restrictions indicated by ElementType enum constants, in line with JLS 9.7.4.

For example, this @Target meta-annotation indicates that the declared type is itself a meta-annotation type. It can only be used on annotation type declarations:

    @Target(ElementType.ANNOTATION_TYPE)
    public @interface MetaAnnotationType {
        ...
    }
 

This @Target meta-annotation indicates that the declared type is intended solely for use as a member type in complex annotation type declarations. It cannot be used to annotate anything directly:

    @Target({})
    public @interface MemberType {
        ...
    }
 

It is a compile-time error for a single ElementType constant to appear more than once in an @Target annotation. For example, the following @Target meta-annotation is illegal:

    @Target({ElementType.FIELD, ElementType.METHOD, ElementType.FIELD})
    public @interface Bogus {
        ...
    }
 

Public Method Summary

ElementType[]

value() Returns an array of the kinds of elements an annotation type can be applied to.

Inherited Method Summary

From interface java.lang.annotation.Annotation

abstract Class<? extends Annotation>	annotationType() Returns the annotation type of this annotation.
abstract boolean	equals(Object obj) Returns true if the specified object represents an annotation that is logically equivalent to this one.
abstract int	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: The hash code of a member-value depends on its type: The hash code of a primitive value v is equal to WrapperType.valueOf(v).hashCode(), where WrapperType is the wrapper type corresponding to the primitive type of v (Byte, Character, Double, Float, Integer, Long, Short, or Boolean).
abstract String	toString() Returns a string representation of this annotation.

Public Methods

public ElementType[] value ()

Returns an array of the kinds of elements an annotation type can be applied to.

Returns

• an array of the kinds of elements an annotation type can be applied to