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 package org.apache.commons.collections4.keyvalue; 18 19 import java.io.Serializable; 20 import java.util.Map; 21 22 import org.apache.commons.collections4.KeyValue; 23 24 /** 25 * A {@link java.util.Map.Entry Map.Entry} tied to a map underneath. 26 * <p> 27 * This can be used to enable a map entry to make changes on the underlying 28 * map, however this will probably mess up any iterators. 29 * </p> 30 * 31 * @param <K> the type of keys 32 * @param <V> the type of mapped values 33 * @since 3.0 34 */ 35 public class TiedMapEntry<K, V> implements Map.Entry<K, V>, KeyValue<K, V>, Serializable { 36 37 /** Serialization version */ 38 private static final long serialVersionUID = -8453869361373831205L; 39 40 /** The map underlying the entry/iterator */ 41 private final Map<K, V> map; 42 43 /** The key */ 44 private final K key; 45 46 /** 47 * Constructs a new entry with the given Map and key. 48 * 49 * @param map the map 50 * @param key the key 51 */ 52 public TiedMapEntry(final Map<K, V> map, final K key) { 53 this.map = map; 54 this.key = key; 55 } 56 57 /** 58 * Compares this {@code Map.Entry} with another {@code Map.Entry}. 59 * <p> 60 * Implemented per API documentation of {@link java.util.Map.Entry#equals(Object)} 61 * 62 * @param obj the object to compare to 63 * @return true if equal key and value 64 */ 65 @Override 66 public boolean equals(final Object obj) { 67 if (obj == this) { 68 return true; 69 } 70 if (!(obj instanceof Map.Entry)) { 71 return false; 72 } 73 final Map.Entry<?, ?> other = (Map.Entry<?, ?>) obj; 74 final Object value = getValue(); 75 return 76 (key == null ? other.getKey() == null : key.equals(other.getKey())) && 77 (value == null ? other.getValue() == null : value.equals(other.getValue())); 78 } 79 80 /** 81 * Gets the key of this entry 82 * 83 * @return the key 84 */ 85 @Override 86 public K getKey() { 87 return key; 88 } 89 90 /** 91 * Gets the value of this entry direct from the map. 92 * 93 * @return the value 94 */ 95 @Override 96 public V getValue() { 97 return map.get(key); 98 } 99 100 /** 101 * Gets a hashCode compatible with the equals method. 102 * <p> 103 * Implemented per API documentation of {@link java.util.Map.Entry#hashCode()} 104 * 105 * @return a suitable hash code 106 */ 107 @Override 108 public int hashCode() { 109 final Object value = getValue(); 110 return (getKey() == null ? 0 : getKey().hashCode()) ^ 111 (value == null ? 0 : value.hashCode()); 112 } 113 114 /** 115 * Sets the value associated with the key direct onto the map. 116 * 117 * @param value the new value 118 * @return the old value 119 * @throws IllegalArgumentException if the value is set to this map entry 120 */ 121 @Override 122 public V setValue(final V value) { 123 if (value == this) { 124 throw new IllegalArgumentException("Cannot set value to this map entry"); 125 } 126 return map.put(key, value); 127 } 128 129 /** 130 * Gets a string version of the entry. 131 * 132 * @return entry as a string 133 */ 134 @Override 135 public String toString() { 136 return getKey() + "=" + getValue(); 137 } 138 139 }