Annotation (Java Platform SE 8 )
Keywords: java.lang.annotation.Annotation interface
Date: 2020-03-26

compact1, compact2, compact3
java.lang.annotation

## Interface Annotation

- All Known Implementing Classes:
    Action, Addressing, BindingType, ConstructorProperties, Deprecated, DescriptorKey, Documented, FaultAction, FunctionalInterface, Generated, HandlerChain, Inherited, InitParam, MTOM, MXBean, Native, Oneway, Override, PostConstruct, PreDestroy, Repeatable, RequestWrapper, Resource, Resources, RespectBinding, ResponseWrapper, Retention, SafeVarargs, ServiceMode, SOAPBinding, SOAPMessageHandler, SOAPMessageHandlers, SupportedAnnotationTypes, SupportedOptions, SupportedSourceVersion, SuppressWarnings, Target, Transient, WebEndpoint, WebFault, WebMethod, WebParam, WebResult, WebService, WebServiceClient, WebServiceFeatureAnnotation, WebServiceProvider, WebServiceRef, WebServiceRefs, XmlAccessorOrder, XmlAccessorType, XmlAnyAttribute, XmlAnyElement, XmlAttachmentRef, XmlAttribute, XmlElement, XmlElementDecl, XmlElementRef, XmlElementRefs, XmlElements, XmlElementWrapper, XmlEnum, XmlEnumValue, XmlID, XmlIDREF, XmlInlineBinaryData, XmlJavaTypeAdapter, XmlJavaTypeAdapters, XmlList, XmlMimeType, XmlMixed, XmlNs, XmlRegistry, XmlRootElement, XmlSchema, XmlSchemaType, XmlSchemaTypes, XmlSeeAlso, XmlTransient, XmlType, XmlValue

      public interface Annotation

  The common interface 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 itself define an annotation type. More information about annotation types can be found in section 9.6 of The Java™ Language Specification. The `AnnotatedElement` interface discusses compatibility concerns when evolving an annotation type from being non-repeatable to being repeatable.
  Since:
    1.5

- - ### Method Summary

    All Methods Instance Methods Abstract Methods
    Modifier and Type | Method and Description
    --- | ---
    `Class<? extends Annotation>` | `annotationType()` Returns the annotation type of this annotation.
    `boolean` | `equals(Object obj)` Returns true if the specified object represents an annotation that is logically equivalent to this one.
    `int` | `hashCode()` Returns the hash code of this annotation, as defined below:
    `String` | `toString()` Returns a string representation of this annotation.

- - ### Method Detail

    - #### equals

          boolean equals(Object obj)

      Returns true if the specified object represents an annotation that is logically equivalent to this one. In other words, returns true if the specified object is an instance of the same annotation type as this instance, all of whose members are equal to the corresponding member of this annotation, as defined below:
      - Two corresponding primitive typed members whose values are `x` and `y` are considered equal if `x == y`, unless their type is `float` or `double`.
      - Two corresponding `float` members whose values are `x` and `y` are considered equal if `Float.valueOf(x).equals(Float.valueOf(y))`. (Unlike the `==` operator, NaN is considered equal to itself, and `0.0f` unequal to `-0.0f`.)
      - Two corresponding `double` members whose values are `x` and `y` are considered equal if `Double.valueOf(x).equals(Double.valueOf(y))`. (Unlike the `==` operator, NaN is considered equal to itself, and `0.0` unequal to `-0.0`.)
      - Two corresponding `String`, `Class`, enum, or annotation typed members whose values are `x` and `y` are considered equal if `x.equals(y)`. (Note that this definition is recursive for annotation typed members.)
      - Two corresponding array typed members `x` and `y` are considered equal if `Arrays.equals(x, y)`, for the appropriate overloading of `Arrays.equals(long[], long[])`.
      Overrides:
        `equals` in class `Object`
      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
      See Also:
        `Object.hashCode()`, `HashMap`

    - #### hashCode

          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`).
      - The hash code of a string, enum, class, or annotation member-value I `v` is computed as by calling `v.hashCode()`. (In the case of annotation member values, this is a recursive definition.)
      - The hash code of an array member-value is computed by calling the appropriate overloading of `Arrays.hashCode` on the value. (There is one overloading for each primitive type, and one for object reference types.)
      Overrides:
        `hashCode` in class `Object`
      Returns:
        the hash code of this annotation
      See Also:
        `Object.equals(java.lang.Object)`, `System.identityHashCode(java.lang.Object)`

    - #### toString

          String toString()

      Returns a string representation of this annotation. The details of the representation are implementation-dependent, but the following may be regarded as typical:

             @com.acme.util.Name(first=Alfred, middle=E., last=Neuman)

      Overrides:
        `toString` in class `Object`
      Returns:
        a string representation of this annotation

    - #### annotationType

          Class<? extends Annotation> annotationType()

      Returns the annotation type of this annotation.
      Returns:
        the annotation type of this annotation

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