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.collections.keyvalue;
18  
19  import java.util.Map;
20  
21  /***
22   * Abstract Pair class to assist with creating correct Map Entry implementations.
23   *
24   * @since Commons Collections 3.0
25   * @version $Revision: 438363 $ $Date: 2006-08-30 05:48:00 +0100 (Wed, 30 Aug 2006) $
26   * 
27   * @author James Strachan
28   * @author Michael A. Smith
29   * @author Neil O'Toole
30   * @author Stephen Colebourne
31   */
32  public abstract class AbstractMapEntry extends AbstractKeyValue implements Map.Entry {
33      
34      /***
35       * Constructs a new entry with the given key and given value.
36       *
37       * @param key  the key for the entry, may be null
38       * @param value  the value for the entry, may be null
39       */
40      protected AbstractMapEntry(Object key, Object value) {
41          super(key, value);
42      }
43  
44      // Map.Entry interface
45      //-------------------------------------------------------------------------
46      /*** 
47       * Sets the value stored in this Map Entry.
48       * <p>
49       * This Map Entry is not connected to a Map, so only the local data is changed.
50       *
51       * @param value  the new value
52       * @return the previous value
53       */
54      public Object setValue(Object value) {
55          Object answer = this.value;
56          this.value = value;
57          return answer;
58      }
59  
60      /***
61       * Compares this Map Entry with another Map Entry.
62       * <p>
63       * Implemented per API documentation of {@link java.util.Map.Entry#equals(Object)}
64       * 
65       * @param obj  the object to compare to
66       * @return true if equal key and value
67       */
68      public boolean equals(Object obj) {
69          if (obj == this) {
70              return true;
71          }
72          if (obj instanceof Map.Entry == false) {
73              return false;
74          }
75          Map.Entry other = (Map.Entry) obj;
76          return
77              (getKey() == null ? other.getKey() == null : getKey().equals(other.getKey())) &&
78              (getValue() == null ? other.getValue() == null : getValue().equals(other.getValue()));
79      }
80       
81      /***
82       * Gets a hashCode compatible with the equals method.
83       * <p>
84       * Implemented per API documentation of {@link java.util.Map.Entry#hashCode()}
85       * 
86       * @return a suitable hash code
87       */
88      public int hashCode() {
89          return (getKey() == null ? 0 : getKey().hashCode()) ^
90                 (getValue() == null ? 0 : getValue().hashCode()); 
91      }
92  
93  }