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Java > Open Source Codes > com > mvnforum > jaxb > db > impl > runtime > IdentityHashSet


1 //
2 // This file was generated by the JavaTM Architecture for XML Binding(JAXB) Reference Implementation, v1.0.5-b16-fcs
3 // See <a HREF="http://java.sun.com/xml/jaxb">http://java.sun.com/xml/jaxb</a>
4 // Any modifications to this file will be lost upon recompilation of the source schema.
5 // Generated on: 2005.12.17 at 09:43:27 AM GMT+07:00
6 //
7
8 package com.mvnforum.jaxb.db.impl.runtime;
9
10 /**
11  * A set of {@link Object}s that uses the == (instead of equals)
12  * for the comparison.
13  *
14  * @author
15  * Kohsuke Kawaguchi (kohsuke.kawaguchi@sun.com)
16  */
17 final class IdentityHashSet {
18     /** The hash table data. */
19     private Object JavaDoc table[];
20
21     /** The total number of mappings in the hash table. */
22     private int count;
23
24     /**
25      * The table is rehashed when its size exceeds this threshold. (The
26      * value of this field is (int)(capacity * loadFactor).)
27      */
28     private int threshold;
29
30     /** The load factor for the hashtable. */
31     private static final float loadFactor = 0.3f;
32     private static final int initialCapacity = 191;
33
34
35     public IdentityHashSet() {
36         table = new Object JavaDoc[initialCapacity];
37         threshold = (int) (initialCapacity * loadFactor);
38     }
39
40     public boolean contains(Object JavaDoc key) {
41         Object JavaDoc tab[] = table;
42         int index = (System.identityHashCode(key) & 0x7FFFFFFF) % tab.length;
43
44         while (true) {
45             final Object JavaDoc e = tab[index];
46             if (e == null)
47                 return false;
48             if (e==key)
49                 return true;
50             index = (index + 1) % tab.length;
51         }
52     }
53
54     /**
55      * rehash.
56      *
57      * It is possible for one thread to call get method
58      * while another thread is performing rehash.
59      * Keep this in mind.
60      */
61     private void rehash() {
62         // create a new table first.
63 // meanwhile, other threads can safely access get method.
64 int oldCapacity = table.length;
65         Object JavaDoc oldMap[] = table;
66
67         int newCapacity = oldCapacity * 2 + 1;
68         Object JavaDoc newMap[] = new Object JavaDoc[newCapacity];
69
70         for (int i = oldCapacity; i-- > 0;)
71             if (oldMap[i] != null) {
72                 int index = (System.identityHashCode(oldMap[i]) & 0x7FFFFFFF) % newMap.length;
73                 while (newMap[index] != null)
74                     index = (index + 1) % newMap.length;
75                 newMap[index] = oldMap[i];
76             }
77
78         // threshold is not accessed by get method.
79 threshold = (int) (newCapacity * loadFactor);
80         // switch!
81 table = newMap;
82     }
83
84     public boolean add(Object JavaDoc newObj) {
85         if (count >= threshold)
86             rehash();
87
88         Object JavaDoc tab[] = table;
89         int index = (System.identityHashCode(newObj) & 0x7FFFFFFF) % tab.length;
90
91         Object JavaDoc existing;
92         
93         while ((existing=tab[index]) != null) {
94             if(existing==newObj) return false;
95             index = (index + 1) % tab.length;
96         }
97         tab[index] = newObj;
98
99         count++;
100         
101         return true;
102     }
103 }
104
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