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Java > Open Source Codes > org > apache > ojb > broker > util > IdentityHashMap


1 package org.apache.ojb.broker.util;
2
3 /* Copyright 2002-2005 The Apache Software Foundation
4  *
5  * Licensed under the Apache License, Version 2.0 (the "License");
6  * you may not use this file except in compliance with the License.
7  * 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
18 import java.util.HashMap JavaDoc;
19 import java.util.Map JavaDoc;
20
21 /**
22  * replacement for the JDK1.4 version
23  * User: Matthew Baird
24  * Date: Jul 8, 2003
25  * Time: 8:37:00 AM
26  */
27 public final class IdentityHashMap extends HashMap JavaDoc
28 {
29     private static final class IdentityKey
30     {
31         private final Object JavaDoc m_key;
32
33         public IdentityKey(final Object JavaDoc key)
34         {
35             m_key = key;
36         }
37
38         public boolean equals(final Object JavaDoc o)
39         {
40             return (o == m_key);
41         }
42
43         public int hashCode()
44         {
45             return System.identityHashCode(m_key);
46         }
47     }
48
49     /**
50      * Constructor for IdentityHashMap.
51      * @param initialCapacity
52      * @param loadFactor
53      */
54     public IdentityHashMap(final int initialCapacity, final float loadFactor)
55     {
56         super(initialCapacity, loadFactor);
57     }
58
59     /**
60      * Constructor for IdentityHashMap.
61      * @param initialCapacity
62      */
63     public IdentityHashMap(final int initialCapacity)
64     {
65         super(initialCapacity);
66     }
67
68     /**
69      * Constructor for IdentityHashMap.
70      */
71     public IdentityHashMap()
72     {
73         super();
74     }
75
76     /**
77      * Constructor for IdentityHashMap.
78      * @param t
79      */
80     public IdentityHashMap(final Map JavaDoc t)
81     {
82         super(t);
83     }
84
85     /**
86      * @see java.util.Map#get(java.lang.Object)
87      */
88     public Object JavaDoc get(final Object JavaDoc key)
89     {
90         return super.get(new IdentityKey(key));
91     }
92
93     /**
94      * @see java.util.Map#put(java.lang.Object, java.lang.Object)
95      */
96     public Object JavaDoc put(final Object JavaDoc key, final Object JavaDoc value)
97     {
98         return super.put(new IdentityKey(key), value);
99     }
100
101     /**
102      * adds an object to the Map. new IdentityKey(obj) is used as key
103      */
104     public Object JavaDoc add(final Object JavaDoc value)
105     {
106         final Object JavaDoc key = new IdentityKey(value);
107         if (!super.containsKey(key))
108         {
109             return super.put(key, value);
110         }
111         else
112         {
113             return null;
114         }
115     }
116
117     /**
118      * @see java.util.Map#remove(java.lang.Object)
119      */
120     public Object JavaDoc remove(final Object JavaDoc key)
121     {
122         return super.remove(new IdentityKey(key));
123     }
124
125     /**
126      * @see java.util.Map#containsKey(java.lang.Object)
127      */
128     public boolean containsKey(final Object JavaDoc key)
129     {
130         return super.containsKey(new IdentityKey(key));
131     }
132 }
133
134
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