1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one or more 3 * contributor license agreements. See the NOTICE file distributed with 4 * this work for additional information regarding copyright ownership. 5 * The ASF licenses this file to You under the Apache License, Version 2.0 6 * (the "License"); you may not use this file except in compliance with 7 * the License. You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17 18 package org.apache.commons.lang3.builder; 19 20 // adapted from org.apache.axis.utils.IDKey 21 22 /** 23 * Wrap an identity key (System.identityHashCode()) 24 * so that an object can only be equal() to itself. 25 * 26 * This is necessary to disambiguate the occasional duplicate 27 * identityHashCodes that can occur. 28 */ 29 final class IDKey { 30 private final Object value; 31 private final int id; 32 33 /** 34 * Constructor for IDKey 35 * @param value The value 36 */ 37 IDKey(final Object value) { 38 // This is the Object hash code 39 this.id = System.identityHashCode(value); 40 // There have been some cases (LANG-459) that return the 41 // same identity hash code for different objects. So 42 // the value is also added to disambiguate these cases. 43 this.value = value; 44 } 45 46 /** 47 * checks if instances are equal 48 * @param other The other object to compare to 49 * @return if the instances are for the same object 50 */ 51 @Override 52 public boolean equals(final Object other) { 53 if (!(other instanceof IDKey)) { 54 return false; 55 } 56 final IDKey idKey = (IDKey) other; 57 if (id != idKey.id) { 58 return false; 59 } 60 // Note that identity equals is used. 61 return value == idKey.value; 62 } 63 64 /** 65 * returns hash code - i.e. the system identity hash code. 66 * @return the hash code 67 */ 68 @Override 69 public int hashCode() { 70 return id; 71 } 72 }