1 | /*
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2 | * Licensed to the Apache Software Foundation (ASF) under one or more
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3 | * contributor license agreements. See the NOTICE file distributed with
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4 | * this work for additional information regarding copyright ownership.
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5 | * The ASF licenses this file to You under the Apache License, Version 2.0
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6 | * (the "License"); you may not use this file except in compliance with
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7 | * the License. You may obtain a copy of the License at
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8 | *
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9 | * http://www.apache.org/licenses/LICENSE-2.0
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10 | *
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11 | * Unless required by applicable law or agreed to in writing, software
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12 | * distributed under the License is distributed on an "AS IS" BASIS,
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13 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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14 | * See the License for the specific language governing permissions and
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15 | * limitations under the License.
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16 | */
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17 |
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18 | /*
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19 | * Note: originally released under the GNU LGPL v2.1,
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20 | * but rereleased by the original author under the ASF license (above).
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21 | */
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22 | package agents.org.apache.commons.lang;
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23 |
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24 | /**
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25 | * <p>A hash map that uses primitive ints for the key rather than objects.</p>
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26 | *
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27 | * <p>Note that this class is for internal optimization purposes only, and may
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28 | * not be supported in future releases of Apache Commons Lang. Utilities of
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29 | * this sort may be included in future releases of Apache Commons Collections.</p>
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30 | *
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31 | * @author Apache Software Foundation
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32 | * @author Justin Couch
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33 | * @author Alex Chaffee (alex@apache.org)
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34 | * @since 2.0
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35 | * @version $Revision: 905857 $
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36 | * @see java.util.HashMap
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37 | */
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38 | class IntHashMap {
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39 |
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40 | /**
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41 | * The hash table data.
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42 | */
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43 | private transient Entry table[];
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44 |
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45 | /**
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46 | * The total number of entries in the hash table.
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47 | */
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48 | private transient int count;
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49 |
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50 | /**
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51 | * The table is rehashed when its size exceeds this threshold. (The
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52 | * value of this field is (int)(capacity * loadFactor).)
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53 | *
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54 | * @serial
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55 | */
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56 | private int threshold;
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57 |
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58 | /**
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59 | * The load factor for the hashtable.
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60 | *
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61 | * @serial
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62 | */
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63 | private final float loadFactor;
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64 |
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65 | /**
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66 | * <p>Innerclass that acts as a datastructure to create a new entry in the
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67 | * table.</p>
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68 | */
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69 | private static class Entry {
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70 | final int hash;
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71 | final int key; // TODO not read; seems to be always same as hash
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72 | Object value;
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73 | Entry next;
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74 |
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75 | /**
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76 | * <p>Create a new entry with the given values.</p>
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77 | *
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78 | * @param hash The code used to hash the object with
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79 | * @param key The key used to enter this in the table
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80 | * @param value The value for this key
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81 | * @param next A reference to the next entry in the table
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82 | */
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83 | protected Entry(int hash, int key, Object value, Entry next) {
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84 | this.hash = hash;
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85 | this.key = key;
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86 | this.value = value;
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87 | this.next = next;
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88 | }
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89 | }
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90 |
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91 | /**
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92 | * <p>Constructs a new, empty hashtable with a default capacity and load
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93 | * factor, which is <code>20</code> and <code>0.75</code> respectively.</p>
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94 | */
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95 | public IntHashMap() {
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96 | this(20, 0.75f);
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97 | }
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98 |
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99 | /**
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100 | * <p>Constructs a new, empty hashtable with the specified initial capacity
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101 | * and default load factor, which is <code>0.75</code>.</p>
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102 | *
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103 | * @param initialCapacity the initial capacity of the hashtable.
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104 | * @throws IllegalArgumentException if the initial capacity is less
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105 | * than zero.
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106 | */
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107 | public IntHashMap(int initialCapacity) {
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108 | this(initialCapacity, 0.75f);
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109 | }
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110 |
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111 | /**
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112 | * <p>Constructs a new, empty hashtable with the specified initial
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113 | * capacity and the specified load factor.</p>
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114 | *
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115 | * @param initialCapacity the initial capacity of the hashtable.
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116 | * @param loadFactor the load factor of the hashtable.
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117 | * @throws IllegalArgumentException if the initial capacity is less
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118 | * than zero, or if the load factor is nonpositive.
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119 | */
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120 | public IntHashMap(int initialCapacity, float loadFactor) {
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121 | super();
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122 | if (initialCapacity < 0) {
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123 | throw new IllegalArgumentException("Illegal Capacity: " + initialCapacity);
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124 | }
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125 | if (loadFactor <= 0) {
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126 | throw new IllegalArgumentException("Illegal Load: " + loadFactor);
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127 | }
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128 | if (initialCapacity == 0) {
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129 | initialCapacity = 1;
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130 | }
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131 |
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132 | this.loadFactor = loadFactor;
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133 | table = new Entry[initialCapacity];
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134 | threshold = (int) (initialCapacity * loadFactor);
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135 | }
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136 |
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137 | /**
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138 | * <p>Returns the number of keys in this hashtable.</p>
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139 | *
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140 | * @return the number of keys in this hashtable.
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141 | */
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142 | public int size() {
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143 | return count;
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144 | }
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145 |
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146 | /**
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147 | * <p>Tests if this hashtable maps no keys to values.</p>
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148 | *
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149 | * @return <code>true</code> if this hashtable maps no keys to values;
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150 | * <code>false</code> otherwise.
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151 | */
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152 | public boolean isEmpty() {
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153 | return count == 0;
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154 | }
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155 |
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156 | /**
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157 | * <p>Tests if some key maps into the specified value in this hashtable.
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158 | * This operation is more expensive than the <code>containsKey</code>
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159 | * method.</p>
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160 | *
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161 | * <p>Note that this method is identical in functionality to containsValue,
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162 | * (which is part of the Map interface in the collections framework).</p>
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163 | *
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164 | * @param value a value to search for.
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165 | * @return <code>true</code> if and only if some key maps to the
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166 | * <code>value</code> argument in this hashtable as
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167 | * determined by the <tt>equals</tt> method;
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168 | * <code>false</code> otherwise.
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169 | * @throws NullPointerException if the value is <code>null</code>.
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170 | * @see #containsKey(int)
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171 | * @see #containsValue(Object)
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172 | * @see java.util.Map
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173 | */
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174 | public boolean contains(Object value) {
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175 | if (value == null) {
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176 | throw new NullPointerException();
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177 | }
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178 |
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179 | Entry tab[] = table;
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180 | for (int i = tab.length; i-- > 0;) {
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181 | for (Entry e = tab[i]; e != null; e = e.next) {
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182 | if (e.value.equals(value)) {
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183 | return true;
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184 | }
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185 | }
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186 | }
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187 | return false;
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188 | }
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189 |
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190 | /**
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191 | * <p>Returns <code>true</code> if this HashMap maps one or more keys
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192 | * to this value.</p>
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193 | *
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194 | * <p>Note that this method is identical in functionality to contains
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195 | * (which predates the Map interface).</p>
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196 | *
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197 | * @param value value whose presence in this HashMap is to be tested.
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198 | * @return boolean <code>true</code> if the value is contained
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199 | * @see java.util.Map
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200 | * @since JDK1.2
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201 | */
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202 | public boolean containsValue(Object value) {
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203 | return contains(value);
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204 | }
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205 |
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206 | /**
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207 | * <p>Tests if the specified object is a key in this hashtable.</p>
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208 | *
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209 | * @param key possible key.
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210 | * @return <code>true</code> if and only if the specified object is a
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211 | * key in this hashtable, as determined by the <tt>equals</tt>
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212 | * method; <code>false</code> otherwise.
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213 | * @see #contains(Object)
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214 | */
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215 | public boolean containsKey(int key) {
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216 | Entry tab[] = table;
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217 | int hash = key;
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218 | int index = (hash & 0x7FFFFFFF) % tab.length;
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219 | for (Entry e = tab[index]; e != null; e = e.next) {
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220 | if (e.hash == hash) {
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221 | return true;
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222 | }
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223 | }
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224 | return false;
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225 | }
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226 |
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227 | /**
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228 | * <p>Returns the value to which the specified key is mapped in this map.</p>
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229 | *
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230 | * @param key a key in the hashtable.
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231 | * @return the value to which the key is mapped in this hashtable;
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232 | * <code>null</code> if the key is not mapped to any value in
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233 | * this hashtable.
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234 | * @see #put(int, Object)
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235 | */
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236 | public Object get(int key) {
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237 | Entry tab[] = table;
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238 | int hash = key;
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239 | int index = (hash & 0x7FFFFFFF) % tab.length;
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240 | for (Entry e = tab[index]; e != null; e = e.next) {
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241 | if (e.hash == hash) {
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242 | return e.value;
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243 | }
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244 | }
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245 | return null;
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246 | }
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247 |
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248 | /**
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249 | * <p>Increases the capacity of and internally reorganizes this
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250 | * hashtable, in order to accommodate and access its entries more
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251 | * efficiently.</p>
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252 | *
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253 | * <p>This method is called automatically when the number of keys
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254 | * in the hashtable exceeds this hashtable's capacity and load
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255 | * factor.</p>
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256 | */
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257 | protected void rehash() {
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258 | int oldCapacity = table.length;
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259 | Entry oldMap[] = table;
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260 |
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261 | int newCapacity = oldCapacity * 2 + 1;
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262 | Entry newMap[] = new Entry[newCapacity];
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263 |
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264 | threshold = (int) (newCapacity * loadFactor);
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265 | table = newMap;
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266 |
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267 | for (int i = oldCapacity; i-- > 0;) {
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268 | for (Entry old = oldMap[i]; old != null;) {
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269 | Entry e = old;
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270 | old = old.next;
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271 |
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272 | int index = (e.hash & 0x7FFFFFFF) % newCapacity;
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273 | e.next = newMap[index];
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274 | newMap[index] = e;
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275 | }
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276 | }
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277 | }
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278 |
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279 | /**
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280 | * <p>Maps the specified <code>key</code> to the specified
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281 | * <code>value</code> in this hashtable. The key cannot be
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282 | * <code>null</code>. </p>
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283 | *
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284 | * <p>The value can be retrieved by calling the <code>get</code> method
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285 | * with a key that is equal to the original key.</p>
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286 | *
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287 | * @param key the hashtable key.
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288 | * @param value the value.
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289 | * @return the previous value of the specified key in this hashtable,
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290 | * or <code>null</code> if it did not have one.
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291 | * @throws NullPointerException if the key is <code>null</code>.
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292 | * @see #get(int)
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293 | */
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294 | public Object put(int key, Object value) {
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295 | // Makes sure the key is not already in the hashtable.
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296 | Entry tab[] = table;
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297 | int hash = key;
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298 | int index = (hash & 0x7FFFFFFF) % tab.length;
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299 | for (Entry e = tab[index]; e != null; e = e.next) {
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300 | if (e.hash == hash) {
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301 | Object old = e.value;
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302 | e.value = value;
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303 | return old;
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304 | }
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305 | }
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306 |
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307 | if (count >= threshold) {
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308 | // Rehash the table if the threshold is exceeded
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309 | rehash();
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310 |
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311 | tab = table;
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312 | index = (hash & 0x7FFFFFFF) % tab.length;
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313 | }
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314 |
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315 | // Creates the new entry.
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316 | Entry e = new Entry(hash, key, value, tab[index]);
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317 | tab[index] = e;
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318 | count++;
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319 | return null;
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320 | }
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321 |
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322 | /**
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323 | * <p>Removes the key (and its corresponding value) from this
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324 | * hashtable.</p>
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325 | *
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326 | * <p>This method does nothing if the key is not present in the
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327 | * hashtable.</p>
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328 | *
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329 | * @param key the key that needs to be removed.
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330 | * @return the value to which the key had been mapped in this hashtable,
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331 | * or <code>null</code> if the key did not have a mapping.
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332 | */
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333 | public Object remove(int key) {
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334 | Entry tab[] = table;
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335 | int hash = key;
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336 | int index = (hash & 0x7FFFFFFF) % tab.length;
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337 | for (Entry e = tab[index], prev = null; e != null; prev = e, e = e.next) {
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338 | if (e.hash == hash) {
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339 | if (prev != null) {
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340 | prev.next = e.next;
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341 | } else {
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342 | tab[index] = e.next;
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343 | }
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344 | count--;
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345 | Object oldValue = e.value;
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346 | e.value = null;
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347 | return oldValue;
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348 | }
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349 | }
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350 | return null;
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351 | }
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352 |
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353 | /**
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354 | * <p>Clears this hashtable so that it contains no keys.</p>
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355 | */
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356 | public synchronized void clear() {
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357 | Entry tab[] = table;
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358 | for (int index = tab.length; --index >= 0;) {
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359 | tab[index] = null;
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360 | }
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361 | count = 0;
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362 | }
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363 |
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364 | }
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