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 */ 017 package org.apache.commons.collections.keyvalue; 018 019 import java.util.Map; 020 021 import org.apache.commons.collections.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 * 030 * @since Commons Collections 3.0 031 * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $ 032 * 033 * @author James Strachan 034 * @author Michael A. Smith 035 * @author Neil O'Toole 036 * @author Stephen Colebourne 037 */ 038 public class DefaultKeyValue extends AbstractKeyValue { 039 040 /** 041 * Constructs a new pair with a null key and null value. 042 */ 043 public DefaultKeyValue() { 044 super(null, null); 045 } 046 047 /** 048 * Constructs a new pair with the specified key and given value. 049 * 050 * @param key the key for the entry, may be null 051 * @param value the value for the entry, may be null 052 */ 053 public DefaultKeyValue(final Object key, final Object value) { 054 super(key, value); 055 } 056 057 /** 058 * Constructs a new pair from the specified <code>KeyValue</code>. 059 * 060 * @param pair the pair to copy, must not be null 061 * @throws NullPointerException if the entry is null 062 */ 063 public DefaultKeyValue(final KeyValue pair) { 064 super(pair.getKey(), pair.getValue()); 065 } 066 067 /** 068 * Constructs a new pair from the specified <code>Map.Entry</code>. 069 * 070 * @param entry the entry to copy, must not be null 071 * @throws NullPointerException if the entry is null 072 */ 073 public DefaultKeyValue(final Map.Entry entry) { 074 super(entry.getKey(), entry.getValue()); 075 } 076 077 //----------------------------------------------------------------------- 078 /** 079 * Sets the key. 080 * 081 * @param key the new key 082 * @return the old key 083 * @throws IllegalArgumentException if key is this object 084 */ 085 public Object setKey(final Object key) { 086 if (key == this) { 087 throw new IllegalArgumentException("DefaultKeyValue may not contain itself as a key."); 088 } 089 090 final Object old = this.key; 091 this.key = key; 092 return old; 093 } 094 095 /** 096 * Sets the value. 097 * 098 * @return the old value of the value 099 * @param value the new value 100 * @throws IllegalArgumentException if value is this object 101 */ 102 public Object setValue(final Object value) { 103 if (value == this) { 104 throw new IllegalArgumentException("DefaultKeyValue may not contain itself as a value."); 105 } 106 107 final Object old = this.value; 108 this.value = value; 109 return old; 110 } 111 112 //----------------------------------------------------------------------- 113 /** 114 * Returns a new <code>Map.Entry</code> object with key and value from this pair. 115 * 116 * @return a MapEntry instance 117 */ 118 public Map.Entry toMapEntry() { 119 return new DefaultMapEntry(this); 120 } 121 122 //----------------------------------------------------------------------- 123 /** 124 * Compares this <code>Map.Entry</code> with another <code>Map.Entry</code>. 125 * <p> 126 * Returns true if the compared object is also a <code>DefaultKeyValue</code>, 127 * and its key and value are equal to this object's key and value. 128 * 129 * @param obj the object to compare to 130 * @return true if equal key and value 131 */ 132 public boolean equals(final Object obj) { 133 if (obj == this) { 134 return true; 135 } 136 if (obj instanceof DefaultKeyValue == false) { 137 return false; 138 } 139 140 DefaultKeyValue other = (DefaultKeyValue) obj; 141 return 142 (getKey() == null ? other.getKey() == null : getKey().equals(other.getKey())) && 143 (getValue() == null ? other.getValue() == null : getValue().equals(other.getValue())); 144 } 145 146 /** 147 * Gets a hashCode compatible with the equals method. 148 * <p> 149 * Implemented per API documentation of {@link java.util.Map.Entry#hashCode()}, 150 * however subclasses may override this. 151 * 152 * @return a suitable hash code 153 */ 154 public int hashCode() { 155 return (getKey() == null ? 0 : getKey().hashCode()) ^ 156 (getValue() == null ? 0 : getValue().hashCode()); 157 } 158 159 }