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.util.Map;
20
21 /**
22 * Abstract Pair class to assist with creating correct
23 * {@link java.util.Map.Entry Map.Entry} implementations.
24 *
25 * @param <K> the type of keys
26 * @param <V> the type of mapped values
27 * @since 3.0
28 */
29 public abstract class AbstractMapEntry<K, V> extends AbstractKeyValue<K, V> implements Map.Entry<K, V> {
30
31 /**
32 * Constructs a new entry with the given key and given value.
33 *
34 * @param key the key for the entry, may be null
35 * @param value the value for the entry, may be null
36 */
37 protected AbstractMapEntry(final K key, final V value) {
38 super(key, value);
39 }
40
41 /**
42 * Compares this {@code Map.Entry} with another {@code Map.Entry}.
43 * <p>
44 * Implemented per API documentation of {@link java.util.Map.Entry#equals(Object)}
45 *
46 * @param obj the object to compare to
47 * @return true if equal key and value
48 */
49 @Override
50 public boolean equals(final Object obj) {
51 if (obj == this) {
52 return true;
53 }
54 if (!(obj instanceof Map.Entry)) {
55 return false;
56 }
57 final Map.Entry<?, ?> other = (Map.Entry<?, ?>) obj;
58 return
59 (getKey() == null ? other.getKey() == null : getKey().equals(other.getKey())) &&
60 (getValue() == null ? other.getValue() == null : getValue().equals(other.getValue()));
61 }
62
63 /**
64 * Gets a hashCode compatible with the equals method.
65 * <p>
66 * Implemented per API documentation of {@link java.util.Map.Entry#hashCode()}
67 *
68 * @return a suitable hash code
69 */
70 @Override
71 public int hashCode() {
72 return (getKey() == null ? 0 : getKey().hashCode()) ^
73 (getValue() == null ? 0 : getValue().hashCode());
74 }
75
76 /**
77 * Sets the value stored in this {@code Map.Entry}.
78 * <p>
79 * This {@code Map.Entry} is not connected to a Map, so only the
80 * local data is changed.
81 *
82 * @param value the new value
83 * @return the previous value
84 */
85 @Override
86 public V setValue(final V value) { // NOPMD
87 return super.setValue(value);
88 }
89
90 }