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annotate graal/com.oracle.max.base/src/com/sun/max/collect/IdentitySet.java @ 4184:fa6b78681c54

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Added copyright check to the gate.
author Doug Simon <doug.simon@oracle.com>
date Tue, 03 Jan 2012 12:37:31 +0100
parents e233f5660da4
children
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1 /*
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2 * Copyright (c) 2007, 2011, Oracle and/or its affiliates. All rights reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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20 * or visit www.oracle.com if you need additional information or have any
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21 * questions.
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22 */
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23 package com.sun.max.collect;
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24
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25 import java.util.*;
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26
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27 import com.sun.max.*;
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28
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29 /**
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30 * Similar to IdentityHashSet, but not recording 'null' as a set member
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31 * and not providing any element removal operations.
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32 *
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33 * (IdentityHashSet's iterator seems to return 'null' as a member even if it has never been entered.)
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34 */
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35 public class IdentitySet<T> implements Iterable<T> {
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36
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37 /**
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38 * The default initial capacity - MUST be a power of two.
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39 */
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40 public static final int DEFAULT_INITIAL_CAPACITY = 16;
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41
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42 /**
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43 * The maximum capacity, used if a higher value is implicitly specified
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44 * by either of the constructors with arguments.
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45 * MUST be a power of two <= 1<<30.
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46 */
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47 public static final int MAXIMUM_CAPACITY = 1 << 30;
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48
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49 // Note: this implementation is partly derived from java.util.HashMap in the standard JDK
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50 // In particular, it uses a table whose length is guaranteed to be a power of 2.
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51
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52 /**
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53 * The number of key-value mappings contained in this map.
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54 */
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55 private int numberOfElements;
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56
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57 /**
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58 * Gets the number of key-value mappings contained in this map.
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59 */
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60 public int numberOfElements() {
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61 return numberOfElements;
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62 }
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63
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64 /**
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65 * The table, resized as necessary. Length MUST Always be a power of two.
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66 */
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67 private T[] table;
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68
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69 /**
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70 * The next size value at which to resize (capacity * load factor).
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71 */
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72 private int threshold;
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73
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74 private void setThreshold() {
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75 if (table.length == 0) {
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76 threshold = -1;
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77 } else {
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78 threshold = (table.length >> 2) * 3;
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79 }
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80 }
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81
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82 /**
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83 * Constructs a new, empty IdentitySet.
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84 */
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85 public IdentitySet() {
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86 this(DEFAULT_INITIAL_CAPACITY);
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87 }
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88
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89 /**
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90 * Constructs a new, empty IdentitySet.
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91 * @param initialCapacity the initial capacity of the Set
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92 * @throws {@code IllegalArgumentException} if {@code initialCapacity} is less than zero}
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93 */
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94 public IdentitySet(int initialCapacity) {
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95 if (initialCapacity < 0) {
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96 throw new IllegalArgumentException();
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97 }
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98 // Find a power of 2 >= initialCapacity
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99 int capacity = Integer.highestOneBit(Math.max(Math.min(MAXIMUM_CAPACITY, initialCapacity), 1));
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100 if (capacity < initialCapacity) {
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101 capacity <<= 1;
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102 }
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103
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104 final Class<T[]> type = null;
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105 table = Utils.cast(type, new Object[capacity]);
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106 setThreshold();
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107 }
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108
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109 private void resize(int newTableLength) {
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110 final T[] oldTable = table;
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111 final Class<T[]> type = null;
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112 table = Utils.cast(type, new Object[newTableLength]);
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113 setThreshold();
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114 numberOfElements = 0;
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115 for (int i = 0; i < oldTable.length; i++) {
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116 final T oldValue = oldTable[i];
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117 if (oldValue != null) {
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118 add(oldValue);
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119 }
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120 }
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121 }
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122
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123 /**
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124 * Applies a supplemental hash function to a given hashCode, which
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125 * defends against poor quality hash functions. This is critical
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126 * because BuckHashMapping uses power-of-two length hash tables, that
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127 * otherwise encounter collisions for hashCodes that do not differ
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128 * in lower bits.
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129 */
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130 static int hash(int hash) {
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131 // This function ensures that hashCodes that differ only by
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132 // constant multiples at each bit position have a bounded
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133 // number of collisions (approximately 8 at default load factor).
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134 final int h = hash ^ ((hash >>> 20) ^ (hash >>> 12));
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135 return h ^ (h >>> 7) ^ (h >>> 4);
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136 }
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137
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138 /**
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139 * Returns index for hash code h.
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140 */
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141 static int indexFor(int h, int length) {
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142 return h & (length - 1);
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143 }
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144
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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145 /**
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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146 * Adds a given element to this set.
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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147 *
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148 * @param element the element to add
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149 * @throws IllegalArgumentException if {@code element == null}
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150 */
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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151 public void add(T element) {
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152 if (element == null) {
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153 throw new IllegalArgumentException("Element cannot be null");
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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154 }
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155 if (numberOfElements > threshold) {
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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156 resize(table.length * 2);
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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157 }
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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158 final int start = indexFor(System.identityHashCode(element), table.length);
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159 int i = start;
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160 do {
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161 final T entry = table[i];
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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162 if (entry == null) {
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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163 table[i] = element;
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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164 numberOfElements++;
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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165 return;
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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166 }
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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167 if (entry == element) {
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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168 return;
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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169 }
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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170 if (++i == table.length) {
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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171 i = 0;
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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172 }
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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173 } while (i != start);
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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174 }
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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175
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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176 /**
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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177 * Determines if a given element is a member of this set.
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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178 *
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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179 * @param element the element to test for membership in this set
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180 * @return {@code true} if {@code element} is in this set, {@code false} otherwise
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181 * @throws IllegalArgumentException if {@code element == null}
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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182 */
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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183 public boolean contains(T element) {
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184 if (element == null) {
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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185 throw new IllegalArgumentException("Element cannot be null");
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
parents:
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186 }
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
parents:
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187 if (numberOfElements == 0) {
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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188 return false;
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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189 }
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
parents:
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190 final int start = indexFor(System.identityHashCode(element), table.length);
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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191 int i = start;
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
parents:
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192 while (true) {
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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193 final T entry = table[i];
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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194 if (entry == element) {
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195 return true;
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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196 }
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
parents:
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197 if (entry == null) {
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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198 return false;
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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199 }
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
parents:
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200 if (++i == table.length) {
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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diff changeset
201 i = 0;
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
parents:
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202 }
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
parents:
diff changeset
203 assert i != start;
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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204 }
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
parents:
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205 }
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
parents:
diff changeset
206
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
parents:
diff changeset
207 public Iterator<T> iterator() {
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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208 final Class<T[]> type = null;
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
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diff changeset
209 final T[] array = Utils.cast(type, new Object[numberOfElements()]);
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
parents:
diff changeset
210 int j = 0;
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
parents:
diff changeset
211 for (int i = 0; i < table.length; i++) {
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
parents:
diff changeset
212 final T element = table[i];
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
parents:
diff changeset
213 if (element != null) {
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
parents:
diff changeset
214 array[j++] = element;
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
parents:
diff changeset
215 }
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
parents:
diff changeset
216 }
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
parents:
diff changeset
217 return Arrays.asList(array).iterator();
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
parents:
diff changeset
218 }
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Thomas Wuerthinger <thomas.wuerthinger@oracle.com>
parents:
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219 }