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 * https://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 import java.util.Map.Entry;
22 import java.util.Objects;
23
24 import org.apache.commons.collections4.KeyValue;
25
26 /**
27 * A {@link Entry Map.Entry} tied to a map underneath.
28 * <p>
29 * This can be used to enable a map entry to make changes on the underlying
30 * map, however this will probably mess up any iterators.
31 * </p>
32 *
33 * @param <K> The type of keys
34 * @param <V> The type of mapped values
35 * @since 3.0
36 */
37 public class TiedMapEntry<K, V> implements Map.Entry<K, V>, KeyValue<K, V>, Serializable {
38
39 /** Serialization version */
40 private static final long serialVersionUID = -8453869361373831205L;
41
42 /** The map underlying the entry/iterator */
43 private final Map<K, V> map;
44
45 /** The key */
46 private final K key;
47
48 /**
49 * Constructs a new entry with the given Map and key.
50 *
51 * @param map The map
52 * @param key The key
53 */
54 public TiedMapEntry(final Map<K, V> map, final K key) {
55 this.map = map;
56 this.key = key;
57 }
58
59 /**
60 * Compares this {@code Map.Entry} with another {@code Map.Entry}.
61 * <p>
62 * Implemented per API documentation of {@link java.util.Map.Entry#equals(Object)}
63 *
64 * @param obj The object to compare to
65 * @return true if equal key and value
66 */
67 @Override
68 public boolean equals(final Object obj) {
69 if (obj == this) {
70 return true;
71 }
72 if (!(obj instanceof Map.Entry)) {
73 return false;
74 }
75 final Map.Entry<?, ?> other = (Map.Entry<?, ?>) obj;
76 return
77 Objects.equals(key, other.getKey()) &&
78 Objects.equals(getValue(), other.getValue());
79 }
80
81 /**
82 * Gets the key of this entry
83 *
84 * @return The key
85 */
86 @Override
87 public K getKey() {
88 return key;
89 }
90
91 /**
92 * Gets the value of this entry direct from the map.
93 *
94 * @return The value
95 */
96 @Override
97 public V getValue() {
98 return map.get(key);
99 }
100
101 /**
102 * Gets a hashCode compatible with the equals method.
103 * <p>
104 * Implemented per API documentation of {@link java.util.Map.Entry#hashCode()}
105 *
106 * @return A suitable hash code
107 */
108 @Override
109 public int hashCode() {
110 final Object value = getValue();
111 return (getKey() == null ? 0 : getKey().hashCode()) ^
112 (value == null ? 0 : value.hashCode());
113 }
114
115 /**
116 * Sets the value associated with the key direct onto the map.
117 *
118 * @param value The new value
119 * @return The old value
120 * @throws IllegalArgumentException if the value is set to this map entry
121 */
122 @Override
123 public V setValue(final V value) {
124 if (value == this) {
125 throw new IllegalArgumentException("Cannot set value to this map entry");
126 }
127 return map.put(key, value);
128 }
129
130 /**
131 * Gets a string version of the entry.
132 *
133 * @return entry as a string
134 */
135 @Override
136 public String toString() {
137 return getKey() + "=" + getValue();
138 }
139
140 }