Java tutorial
/* * Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package java.lang.annotation; /** * The common interface extended by all annotation types. Note that an * interface that manually extends this one does <i>not</i> 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 * <cite>The Java™ Language Specification</cite>. * * The {@link java.lang.reflect.AnnotatedElement} interface discusses * compatibility concerns when evolving an annotation type from being * non-repeatable to being repeatable. * * @author Josh Bloch * @since 1.5 */ public interface Annotation { /** * 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: * <ul> * <li>Two corresponding primitive typed members whose values are * {@code x} and {@code y} are considered equal if {@code x == y}, * unless their type is {@code float} or {@code double}. * * <li>Two corresponding {@code float} members whose values * are {@code x} and {@code y} are considered equal if * {@code Float.valueOf(x).equals(Float.valueOf(y))}. * (Unlike the {@code ==} operator, NaN is considered equal * to itself, and {@code 0.0f} unequal to {@code -0.0f}.) * * <li>Two corresponding {@code double} members whose values * are {@code x} and {@code y} are considered equal if * {@code Double.valueOf(x).equals(Double.valueOf(y))}. * (Unlike the {@code ==} operator, NaN is considered equal * to itself, and {@code 0.0} unequal to {@code -0.0}.) * * <li>Two corresponding {@code String}, {@code Class}, enum, or * annotation typed members whose values are {@code x} and {@code y} * are considered equal if {@code x.equals(y)}. (Note that this * definition is recursive for annotation typed members.) * * <li>Two corresponding array typed members {@code x} and {@code y} * are considered equal if {@code Arrays.equals(x, y)}, for the * appropriate overloading of {@link java.util.Arrays#equals}. * </ul> * * @return true if the specified object represents an annotation * that is logically equivalent to this one, otherwise false */ boolean equals(Object obj); /** * Returns the hash code of this annotation, as defined below: * * <p>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 {@link String#hashCode()}) XOR * the hash code of the member-value, as defined below: * * <p>The hash code of a member-value depends on its type: * <ul> * <li>The hash code of a primitive value <i>{@code v}</i> is equal to * <code><i>WrapperType</i>.valueOf(<i>v</i>).hashCode()</code>, where * <i>{@code WrapperType}</i> is the wrapper type corresponding * to the primitive type of <i>{@code v}</i> ({@link Byte}, * {@link Character}, {@link Double}, {@link Float}, {@link Integer}, * {@link Long}, {@link Short}, or {@link Boolean}). * * <li>The hash code of a string, enum, class, or annotation member-value I <i>{@code v}</i> is computed as by calling * <code><i>v</i>.hashCode()</code>. (In the case of annotation * member values, this is a recursive definition.) * * <li>The hash code of an array member-value is computed by calling * the appropriate overloading of * {@link java.util.Arrays#hashCode(long[]) Arrays.hashCode} * on the value. (There is one overloading for each primitive * type, and one for object reference types.) * </ul> * * @return the hash code of this annotation */ int hashCode(); /** * Returns a string representation of this annotation. The details * of the representation are implementation-dependent, but the following * may be regarded as typical: * <pre> * @com.acme.util.Name(first=Alfred, middle=E., last=Neuman) * </pre> * * @return a string representation of this annotation */ String toString(); /** * Returns the annotation type of this annotation. * @return the annotation type of this annotation */ Class<? extends Annotation> annotationType(); }