1 /* 2 * Copyright (c) 2017, 2018, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * The Universal Permissive License (UPL), Version 1.0 6 * 7 * Subject to the condition set forth below, permission is hereby granted to any 8 * person obtaining a copy of this software, associated documentation and/or 9 * data (collectively the "Software"), free of charge and under any and all 10 * copyright rights in the Software, and any and all patent rights owned or 11 * freely licensable by each licensor hereunder covering either (i) the 12 * unmodified Software as contributed to or provided by such licensor, or (ii) 13 * the Larger Works (as defined below), to deal in both 14 * 15 * (a) the Software, and 16 * 17 * (b) any piece of software and/or hardware listed in the lrgrwrks.txt file if 18 * one is included with the Software each a "Larger Work" to which the Software 19 * is contributed by such licensors), 20 * 21 * without restriction, including without limitation the rights to copy, create 22 * derivative works of, display, perform, and distribute the Software and make, 23 * use, sell, offer for sale, import, export, have made, and have sold the 24 * Software and the Larger Work(s), and to sublicense the foregoing rights on 25 * either these or other terms. 26 * 27 * This license is subject to the following condition: 28 * 29 * The above copyright notice and either this complete permission notice or at a 30 * minimum a reference to the UPL must be included in all copies or substantial 31 * portions of the Software. 32 * 33 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 34 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 35 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 36 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 37 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 38 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 39 * SOFTWARE. 40 */ 41 package jdk.internal.vm.compiler.collections; 42 43 /** 44 * Strategy for comparing two objects. Default predefined strategies are {@link #DEFAULT}, 45 * {@link #IDENTITY}, and {@link #IDENTITY_WITH_SYSTEM_HASHCODE}. 46 * 47 * @since 1.0 48 */ 49 public abstract class Equivalence { 50 51 /** 52 * Default equivalence calling {@link #equals(Object)} to check equality and {@link #hashCode()} 53 * for obtaining hash values. Do not change the logic of this class as it may be inlined in 54 * other places. 55 * 56 * @since 1.0 57 */ 58 public static final Equivalence DEFAULT = new Equivalence() { 59 60 @Override 61 public boolean equals(Object a, Object b) { 62 return a.equals(b); 63 } 64 65 @Override 66 public int hashCode(Object o) { 67 return o.hashCode(); 68 } 69 }; 70 71 /** 72 * Identity equivalence using {@code ==} to check equality and {@link #hashCode()} for obtaining 73 * hash values. Do not change the logic of this class as it may be inlined in other places. 74 * 75 * @since 1.0 76 */ 77 public static final Equivalence IDENTITY = new Equivalence() { 78 79 @Override 80 public boolean equals(Object a, Object b) { 81 return a == b; 82 } 83 84 @Override 85 public int hashCode(Object o) { 86 return o.hashCode(); 87 } 88 }; 89 90 /** 91 * Identity equivalence using {@code ==} to check equality and 92 * {@link System#identityHashCode(Object)} for obtaining hash values. Do not change the logic of 93 * this class as it may be inlined in other places. 94 * 95 * @since 1.0 96 */ 97 public static final Equivalence IDENTITY_WITH_SYSTEM_HASHCODE = new Equivalence() { 98 99 @Override 100 public boolean equals(Object a, Object b) { 101 return a == b; 102 } 103 104 @Override 105 public int hashCode(Object o) { 106 return System.identityHashCode(o); 107 } 108 }; 109 110 /** 111 * Subclass for creating custom equivalence definitions. 112 * 113 * @since 1.0 114 */ 115 protected Equivalence() { 116 } 117 118 /** 119 * Returns {@code true} if the non-{@code null} arguments are equal to each other and 120 * {@code false} otherwise. 121 * 122 * @since 1.0 123 */ 124 public abstract boolean equals(Object a, Object b); 125 126 /** 127 * Returns the hash code of a non-{@code null} argument {@code o}. 128 * 129 * @since 1.0 130 */ 131 public abstract int hashCode(Object o); 132 }