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Java > Open Source Codes > org > jaxen > expr > IdentitySet


1 /*
2  $Id$
3
4  Copyright 2005 Elliotte Rusty Harold. All Rights Reserved.
5  
6  Redistribution and use of this software and associated documentation
7  ("Software"), with or without modification, are permitted provided
8  that the following conditions are met:
9
10  1. Redistributions of source code must retain copyright
11     statements and notices. Redistributions must also contain a
12     copy of this document.
13  
14  2. Redistributions in binary form must reproduce the
15     above copyright notice, this list of conditions and the
16     following disclaimer in the documentation and/or other
17     materials provided with the distribution.
18  
19  3. The name "jaxen" must not be used to endorse or promote
20     products derived from this Software without prior written
21     permission of The Werken Company. For written permission,
22     please contact bob@werken.com.
23  
24  4. Products derived from this Software may not be called "jaxen"
25     nor may "jaxen" appear in their names without prior written
26     permission of The Werken Company. "jaxen" is a registered
27     trademark of The Werken Company.
28  
29  5. Due credit should be given to The Werken Company.
30     (http://jaxen.werken.com/).
31  
32  THIS SOFTWARE IS PROVIDED BY THE WERKEN COMPANY AND CONTRIBUTORS
33  ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT
34  NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
35  FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
36  THE WERKEN COMPANY OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
37  INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
38  (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
39  SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
40  HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
41  STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
42  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
43  OF THE POSSIBILITY OF SUCH DAMAGE.
44
45  */
46 package org.jaxen.expr;
47
48 import java.util.HashSet JavaDoc;
49
50
51 /**
52  * <p>
53  * This is a set that uses identity rather than equality semantics.
54  * </p>
55  *
56  * @author Elliotte Rusty Harold
57  *
58  */
59 final class IdentitySet {
60
61     private HashSet JavaDoc contents = new HashSet JavaDoc();
62     
63     IdentitySet() {
64         super();
65     }
66
67     void add(Object JavaDoc object) {
68         IdentityWrapper wrapper = new IdentityWrapper(object);
69         contents.add(wrapper);
70     }
71
72     public boolean contains(Object JavaDoc object) {
73         IdentityWrapper wrapper = new IdentityWrapper(object);
74         return contents.contains(wrapper);
75     }
76     
77     private static class IdentityWrapper {
78
79         private Object JavaDoc object;
80         
81         IdentityWrapper(Object JavaDoc object) {
82             this.object = object;
83         }
84         
85         public boolean equals(Object JavaDoc o) {
86             IdentityWrapper w = (IdentityWrapper) o;
87             return object == w.object;
88         }
89
90         public int hashCode() {
91             return System.identityHashCode(object);
92         }
93
94     }
95
96
97 }
98
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