1 | /*
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2 | * JOSMng - a Java Open Street Map editor, the next generation.
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3 | *
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4 | * Copyright (C) 2008 Petr Nejedly <P.Nejedly@sh.cvut.cz>
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5 | *
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6 | * This program is free software; you can redistribute it and/or modify
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7 | * it under the terms of the GNU General Public License as published by
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8 | * the Free Software Foundation; either version 2 of the License, or
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9 | * (at your option) any later version.
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10 | *
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11 | * This program is distributed in the hope that it will be useful,
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12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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14 | * GNU General Public License for more details.
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15 |
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16 | * You should have received a copy of the GNU General Public License along
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17 | * with this program; if not, write to the Free Software Foundation, Inc.,
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18 | * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
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19 | */
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20 |
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21 | package org.openstreetmap.josm.tools;
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22 |
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23 | import java.util.AbstractList;
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24 | import java.util.ConcurrentModificationException;
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25 | import java.util.Iterator;
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26 | import java.util.NoSuchElementException;
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27 | import java.util.RandomAccess;
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28 |
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29 | /**
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30 | * A List implementation initially based on given array, but never modifying
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31 | * the array directly. On the first modification, the implementation will
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32 | * create its own copy of the array, and after that it behaves mostly as
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33 | * an ArrayList.
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34 | *
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35 | * @author nenik
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36 | */
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37 | public final class CopyList<E> extends AbstractList<E> implements RandomAccess, Cloneable {
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38 | private E[] array;
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39 | private int size;
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40 | private boolean pristine;
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41 |
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42 | /**
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43 | * Create a List over given array.
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44 | * @param array The initial List content. The array is never modified
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45 | * by the {@code CopyList}.
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46 | */
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47 | public CopyList(E[] array) {
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48 | this(array, array.length);
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49 | }
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50 |
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51 | public CopyList(E[] array, int size) {
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52 | this.array = array;
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53 | this.size = size;
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54 | pristine = true;
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55 | }
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56 |
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57 | // read-only access:
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58 | public @Override E get(int index) {
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59 | rangeCheck(index);
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60 | return array[index];
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61 | }
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62 |
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63 | public @Override int size() {
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64 | return size;
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65 | }
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66 |
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67 | // modification:
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68 | public @Override E set(int index, E element) {
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69 | rangeCheck(index);
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70 | changeCheck();
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71 |
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72 | E old = array[index];
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73 | array[index] = element;
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74 | return old;
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75 | }
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76 |
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77 | // full resizable semantics:
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78 | public @Override void add(int index, E element) {
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79 | // range check
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80 | ensureCapacity(size+1);
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81 | changeCheck();
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82 |
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83 | System.arraycopy(array, index, array, index+1, size-index);
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84 | array[index] = element;
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85 | size++;
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86 | }
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87 |
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88 | public @Override E remove(int index) {
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89 | rangeCheck(index);
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90 | changeCheck();
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91 |
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92 | modCount++;
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93 | E element = array[index];
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94 | if (index < size-1) {
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95 | System.arraycopy(array, index+1, array, index, size-index-1);
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96 | } else {
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97 | array[index] = null;
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98 | }
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99 | size--;
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100 | return element;
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101 | }
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102 |
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103 | // speed optimizations:
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104 | public @Override boolean add(E element) {
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105 | ensureCapacity(size+1);
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106 | changeCheck();
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107 | array[size++] = element;
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108 | return true;
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109 | }
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110 |
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111 | public @Override void clear() {
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112 | modCount++;
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113 |
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114 | // clean up the array
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115 | while (size > 0) {
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116 | array[--size] = null;
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117 | }
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118 | }
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119 |
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120 | // helpers:
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121 | /**
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122 | * Returns another independent copy-on-write copy of this <tt>List</tt>
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123 | * instance. Neither the elements nor the backing storage are copied.
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124 | *
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125 | * @return a clone of this <tt>CopyList</tt> instance
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126 | */
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127 | public @Override Object clone() {
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128 | return new CopyList<E>(array, size);
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129 | }
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130 |
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131 | private void rangeCheck(int index) {
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132 | if (index >= size || index < 0) throw new IndexOutOfBoundsException("Index:" + index + " Size:" + size);
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133 | }
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134 |
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135 | private void changeCheck() {
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136 | if (pristine) {
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137 | array = array.clone();
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138 | pristine = false;
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139 | }
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140 | }
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141 |
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142 | @SuppressWarnings("unchecked")
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143 | private void ensureCapacity(int target) {
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144 | modCount++;
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145 | if (target > array.length) {
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146 | E[] old = array;
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147 |
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148 | int newCapacity = Math.max(target, (array.length * 3)/2 + 1);
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149 | array = (E[]) new Object[newCapacity];
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150 | System.arraycopy(old, 0, array, 0, size);
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151 | pristine = false;
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152 | }
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153 | }
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154 |
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155 | @Override
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156 | public Iterator<E> iterator() {
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157 | return new Itr();
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158 | }
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159 |
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160 | private class Itr implements Iterator<E> {
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161 | /**
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162 | * Index of element to be returned by subsequent call to next.
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163 | */
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164 | int cursor = 0;
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165 |
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166 | /**
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167 | * Index of element returned by most recent call to next or
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168 | * previous. Reset to -1 if this element is deleted by a call
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169 | * to remove.
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170 | */
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171 | int lastRet = -1;
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172 |
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173 | /**
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174 | * The modCount value that the iterator believes that the backing
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175 | * List should have. If this expectation is violated, the iterator
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176 | * has detected concurrent modification.
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177 | */
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178 | int expectedModCount = modCount;
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179 |
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180 | public boolean hasNext() {
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181 | return cursor != size;
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182 | }
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183 |
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184 | public E next() {
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185 | checkForComodification();
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186 | try {
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187 | E next = array[cursor];
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188 | lastRet = cursor++;
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189 | return next;
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190 | } catch (IndexOutOfBoundsException e) {
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191 | checkForComodification();
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192 | throw new NoSuchElementException();
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193 | }
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194 | }
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195 |
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196 | public void remove() {
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197 | if (lastRet == -1)
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198 | throw new IllegalStateException();
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199 | checkForComodification();
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200 |
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201 | try {
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202 | CopyList.this.remove(lastRet);
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203 | if (lastRet < cursor) {
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204 | cursor--;
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205 | }
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206 | lastRet = -1;
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207 | expectedModCount = modCount;
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208 | } catch (IndexOutOfBoundsException e) {
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209 | throw new ConcurrentModificationException();
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210 | }
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211 | }
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212 |
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213 | final void checkForComodification() {
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214 | if (modCount != expectedModCount)
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215 | throw new ConcurrentModificationException();
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216 | }
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217 | }
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218 |
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219 | }
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