001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017package org.apache.commons.collections4.keyvalue; 018 019import java.util.Map; 020 021import org.apache.commons.collections4.KeyValue; 022 023/** 024 * A mutable <code>KeyValue</code> pair that does not implement 025 * {@link java.util.Map.Entry Map.Entry}. 026 * <p> 027 * Note that a <code>DefaultKeyValue</code> instance may not contain 028 * itself as a key or value. 029 * </p> 030 * 031 * @param <K> the type of keys 032 * @param <V> the type of values 033 * @since 3.0 034 */ 035public class DefaultKeyValue<K, V> extends AbstractKeyValue<K, V> { 036 037 /** 038 * Constructs a new pair with a null key and null value. 039 */ 040 public DefaultKeyValue() { 041 super(null, null); 042 } 043 044 /** 045 * Constructs a new pair with the specified key and given value. 046 * 047 * @param key the key for the entry, may be null 048 * @param value the value for the entry, may be null 049 */ 050 public DefaultKeyValue(final K key, final V value) { 051 super(key, value); 052 } 053 054 /** 055 * Constructs a new pair from the specified <code>KeyValue</code>. 056 * 057 * @param pair the pair to copy, must not be null 058 * @throws NullPointerException if the entry is null 059 */ 060 public DefaultKeyValue(final KeyValue<? extends K, ? extends V> pair) { 061 super(pair.getKey(), pair.getValue()); 062 } 063 064 /** 065 * Constructs a new pair from the specified <code>Map.Entry</code>. 066 * 067 * @param entry the entry to copy, must not be null 068 * @throws NullPointerException if the entry is null 069 */ 070 public DefaultKeyValue(final Map.Entry<? extends K, ? extends V> entry) { 071 super(entry.getKey(), entry.getValue()); 072 } 073 074 //----------------------------------------------------------------------- 075 /** 076 * Sets the key. 077 * 078 * @param key the new key 079 * @return the old key 080 * @throws IllegalArgumentException if key is this object 081 */ 082 @Override 083 public K setKey(final K key) { 084 if (key == this) { 085 throw new IllegalArgumentException("DefaultKeyValue may not contain itself as a key."); 086 } 087 088 return super.setKey(key); 089 } 090 091 /** 092 * Sets the value. 093 * 094 * @return the old value of the value 095 * @param value the new value 096 * @throws IllegalArgumentException if value is this object 097 */ 098 @Override 099 public V setValue(final V value) { 100 if (value == this) { 101 throw new IllegalArgumentException("DefaultKeyValue may not contain itself as a value."); 102 } 103 104 return super.setValue(value); 105 } 106 107 //----------------------------------------------------------------------- 108 /** 109 * Returns a new <code>Map.Entry</code> object with key and value from this pair. 110 * 111 * @return a MapEntry instance 112 */ 113 public Map.Entry<K, V> toMapEntry() { 114 return new DefaultMapEntry<>(this); 115 } 116 117 //----------------------------------------------------------------------- 118 /** 119 * Compares this <code>Map.Entry</code> with another <code>Map.Entry</code>. 120 * <p> 121 * Returns true if the compared object is also a <code>DefaultKeyValue</code>, 122 * and its key and value are equal to this object's key and value. 123 * 124 * @param obj the object to compare to 125 * @return true if equal key and value 126 */ 127 @Override 128 public boolean equals(final Object obj) { 129 if (obj == this) { 130 return true; 131 } 132 if (obj instanceof DefaultKeyValue == false) { 133 return false; 134 } 135 136 final DefaultKeyValue<?, ?> other = (DefaultKeyValue<?, ?>) obj; 137 return 138 (getKey() == null ? other.getKey() == null : getKey().equals(other.getKey())) && 139 (getValue() == null ? other.getValue() == null : getValue().equals(other.getValue())); 140 } 141 142 /** 143 * Gets a hashCode compatible with the equals method. 144 * <p> 145 * Implemented per API documentation of {@link java.util.Map.Entry#hashCode()}, 146 * however subclasses may override this. 147 * 148 * @return a suitable hash code 149 */ 150 @Override 151 public int hashCode() { 152 return (getKey() == null ? 0 : getKey().hashCode()) ^ 153 (getValue() == null ? 0 : getValue().hashCode()); 154 } 155 156}