java.lang.annotation.Annotation Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with this
* work for additional information regarding copyright ownership. The ASF
* licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
package java.lang.annotation;
/**
* Defines the interface implemented by all annotations. Note that the interface
* itself is not an annotation, and neither is an interface that simply
* extends this one. Only the compiler is able to create proper annotation
* types.
*
* @since 1.5
*/
public interface Annotation {
/**
* Returns the type of this annotation.
*
* @return A {@code Class} instance representing the annotation type.
*/
Class annotationType();
/**
* Determines whether or not this annotation is equivalent to the annotation
* passed. This is determined according to the following rules:
*
*
* -
* Two annotations {@code x} and {@code y} are equal if and only if
* they are members of the same annotation type and all the member
* values of {@code x} are equal to the corresponding member values
* of {@code y}.
*
* -
* The equality of primitive member values {@code x} and {@code y}
* is determined (in a way similar to) using the corresponding
* wrapper classes. For example,
* {@code Integer.valueOf(x).equals(Integer.valueOf(y)} is used for
* {@code int} values. Note: The behavior is identical to the
* {@code ==} operator for all but the floating point type, so the
* implementation may as well use {@code ==} in these cases for
* performance reasons. Only for the {@code float} and {@code double}
* types the result will be slightly different: {@code NaN} is equal
* to {@code NaN}, and {@code -0.0} is equal to {@code 0.0}, both of
* which is normally not the case.
*
* -
* The equality of two array member values {@code x} and {@code y}
* is determined using the corresponding {@code equals(x, y)}
* helper function in {@link java.util.Arrays}.
*
* -
* The hash code for all other member values is determined by simply
* calling their {@code equals()} method.
*
*
*
* @param obj
* The object to compare to.
*
* @return {@code true} if {@code obj} is equal to this annotation,
* {@code false} otherwise.
*/
boolean equals(Object obj);
/**
* Returns the hash code of this annotation. The hash code is determined
* according to the following rules:
*
*
* -
* The hash code of an annotation is the sum of the hash codes of
* its annotation members.
*
* -
* The hash code of an annotation member is calculated as {@code
* (0x7f * n.hashCode()) ^ v.hashCode())}, where {@code n} is the
* name of the member (as a {@code String}) and {@code v} its value.
*
* -
* The hash code for a primitive member value is determined using
* the corresponding wrapper type. For example, {@code
* Integer.valueOf(v).hashCode()} is used for an {@code int} value
* {@code v}.
*
* -
* The hash code for an array member value {@code v} is determined
* using the corresponding {@code hashCode(v)} helper function in
* {@link java.util.Arrays}.
*
* -
* The hash code for all other member values is determined by simply
* calling their {@code hashCode} method.
*
*
*
* @return the hash code.
*/
int hashCode();
/**
* Returns a {@code String} representation of this annotation. It is not
* strictly defined what the representation has to look like, but it usually
* consists of the name of the annotation, preceded by a "@". If the
* annotation contains field members, their names and values are also
* included in the result.
*
* @return the {@code String} that represents this annotation.
*/
String toString();
}