View Javadoc
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      // Map.Entry interface
42      //-------------------------------------------------------------------------
43      /**
44       * Sets the value stored in this <code>Map.Entry</code>.
45       * <p>
46       * This <code>Map.Entry</code> is not connected to a Map, so only the
47       * local data is changed.
48       *
49       * @param value  the new value
50       * @return the previous value
51       */
52      @Override
53      public V setValue(final V value) { // NOPMD
54          return super.setValue(value);
55      }
56  
57      /**
58       * Compares this <code>Map.Entry</code> with another <code>Map.Entry</code>.
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 == false) {
71              return false;
72          }
73          final Map.Entry<?, ?> other = (Map.Entry<?, ?>) obj;
74          return
75              (getKey() == null ? other.getKey() == null : getKey().equals(other.getKey())) &&
76              (getValue() == null ? other.getValue() == null : getValue().equals(other.getValue()));
77      }
78  
79      /**
80       * Gets a hashCode compatible with the equals method.
81       * <p>
82       * Implemented per API documentation of {@link java.util.Map.Entry#hashCode()}
83       *
84       * @return a suitable hash code
85       */
86      @Override
87      public int hashCode() {
88          return (getKey() == null ? 0 : getKey().hashCode()) ^
89                 (getValue() == null ? 0 : getValue().hashCode());
90      }
91  
92  }