[6380] | 1 | // License: GPL. For details, see LICENSE file.
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[1862] | 2 | package org.openstreetmap.josm.tools;
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| 3 |
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| 4 | import java.util.AbstractList;
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[6717] | 5 | import java.util.Arrays;
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[2741] | 6 | import java.util.ConcurrentModificationException;
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| 7 | import java.util.Iterator;
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| 8 | import java.util.NoSuchElementException;
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[1862] | 9 | import java.util.RandomAccess;
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| 10 |
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| 11 | /**
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| 12 | * A List implementation initially based on given array, but never modifying
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| 13 | * the array directly. On the first modification, the implementation will
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| 14 | * create its own copy of the array, and after that it behaves mostly as
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| 15 | * an ArrayList.
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| 16 | *
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| 17 | * @author nenik
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| 18 | */
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[2741] | 19 | public final class CopyList<E> extends AbstractList<E> implements RandomAccess, Cloneable {
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[1862] | 20 | private E[] array;
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| 21 | private int size;
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| 22 | private boolean pristine;
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| 23 |
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| 24 | /**
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| 25 | * Create a List over given array.
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| 26 | * @param array The initial List content. The array is never modified
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| 27 | * by the {@code CopyList}.
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| 28 | */
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| 29 | public CopyList(E[] array) {
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| 30 | this(array, array.length);
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| 31 | }
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| 32 |
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[2907] | 33 | public CopyList(E[] array, int size) {
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[1862] | 34 | this.array = array;
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| 35 | this.size = size;
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| 36 | pristine = true;
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| 37 | }
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| 38 |
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| 39 | // read-only access:
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[6362] | 40 | @Override
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| 41 | public E get(int index) {
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[1862] | 42 | rangeCheck(index);
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| 43 | return array[index];
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| 44 | }
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| 45 |
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[6362] | 46 | @Override
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| 47 | public int size() {
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[1862] | 48 | return size;
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| 49 | }
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| 50 |
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| 51 | // modification:
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[6362] | 52 | @Override
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| 53 | public E set(int index, E element) {
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[1862] | 54 | rangeCheck(index);
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| 55 | changeCheck();
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| 56 |
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| 57 | E old = array[index];
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| 58 | array[index] = element;
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| 59 | return old;
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| 60 | }
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| 61 |
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| 62 | // full resizable semantics:
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[6362] | 63 | @Override
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| 64 | public void add(int index, E element) {
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[1862] | 65 | // range check
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| 66 | ensureCapacity(size+1);
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| 67 | changeCheck();
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| 68 |
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| 69 | System.arraycopy(array, index, array, index+1, size-index);
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| 70 | array[index] = element;
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| 71 | size++;
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| 72 | }
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| 73 |
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[6362] | 74 | @Override
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| 75 | public E remove(int index) {
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[1862] | 76 | rangeCheck(index);
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| 77 | changeCheck();
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| 78 |
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| 79 | modCount++;
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| 80 | E element = array[index];
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| 81 | if (index < size-1) {
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| 82 | System.arraycopy(array, index+1, array, index, size-index-1);
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| 83 | } else {
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| 84 | array[index] = null;
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| 85 | }
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| 86 | size--;
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| 87 | return element;
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| 88 | }
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| 89 |
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| 90 | // speed optimizations:
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[6362] | 91 | @Override
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| 92 | public boolean add(E element) {
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[1862] | 93 | ensureCapacity(size+1);
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| 94 | changeCheck();
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| 95 | array[size++] = element;
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| 96 | return true;
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| 97 | }
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| 98 |
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[6362] | 99 | @Override
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| 100 | public void clear() {
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[2741] | 101 | modCount++;
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[1862] | 102 |
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| 103 | // clean up the array
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[2741] | 104 | while (size > 0) {
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| 105 | array[--size] = null;
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| 106 | }
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[1862] | 107 | }
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| 108 |
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| 109 | // helpers:
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| 110 | /**
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| 111 | * Returns another independent copy-on-write copy of this <tt>List</tt>
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| 112 | * instance. Neither the elements nor the backing storage are copied.
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| 113 | *
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| 114 | * @return a clone of this <tt>CopyList</tt> instance
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| 115 | */
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[6362] | 116 | @Override
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| 117 | public Object clone() {
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[7005] | 118 | return new CopyList<>(array, size);
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[1862] | 119 | }
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| 120 |
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| 121 | private void rangeCheck(int index) {
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[2930] | 122 | if (index >= size || index < 0) throw new IndexOutOfBoundsException("Index:" + index + " Size:" + size);
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[1862] | 123 | }
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| 124 |
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| 125 | private void changeCheck() {
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| 126 | if (pristine) {
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| 127 | array = array.clone();
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| 128 | pristine = false;
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| 129 | }
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| 130 | }
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| 131 |
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| 132 | private void ensureCapacity(int target) {
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| 133 | modCount++;
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| 134 | if (target > array.length) {
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| 135 | int newCapacity = Math.max(target, (array.length * 3)/2 + 1);
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[6717] | 136 | array = Arrays.copyOf(array, newCapacity);
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[1862] | 137 | pristine = false;
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[2741] | 138 | }
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[1862] | 139 | }
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[2741] | 140 |
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| 141 | @Override
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| 142 | public Iterator<E> iterator() {
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| 143 | return new Itr();
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[1862] | 144 | }
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[2741] | 145 |
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| 146 | private class Itr implements Iterator<E> {
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| 147 | /**
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| 148 | * Index of element to be returned by subsequent call to next.
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| 149 | */
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| 150 | int cursor = 0;
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| 151 |
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| 152 | /**
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| 153 | * Index of element returned by most recent call to next or
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| 154 | * previous. Reset to -1 if this element is deleted by a call
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| 155 | * to remove.
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| 156 | */
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| 157 | int lastRet = -1;
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| 158 |
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| 159 | /**
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| 160 | * The modCount value that the iterator believes that the backing
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| 161 | * List should have. If this expectation is violated, the iterator
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| 162 | * has detected concurrent modification.
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| 163 | */
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| 164 | int expectedModCount = modCount;
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| 165 |
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[6084] | 166 | @Override
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[2741] | 167 | public boolean hasNext() {
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| 168 | return cursor != size;
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| 169 | }
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| 170 |
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[6084] | 171 | @Override
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[2741] | 172 | public E next() {
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| 173 | checkForComodification();
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| 174 | try {
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| 175 | E next = array[cursor];
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| 176 | lastRet = cursor++;
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| 177 | return next;
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| 178 | } catch (IndexOutOfBoundsException e) {
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| 179 | checkForComodification();
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| 180 | throw new NoSuchElementException();
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| 181 | }
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| 182 | }
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| 183 |
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[6084] | 184 | @Override
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[2741] | 185 | public void remove() {
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| 186 | if (lastRet == -1)
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| 187 | throw new IllegalStateException();
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| 188 | checkForComodification();
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| 189 |
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| 190 | try {
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| 191 | CopyList.this.remove(lastRet);
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| 192 | if (lastRet < cursor) {
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| 193 | cursor--;
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| 194 | }
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| 195 | lastRet = -1;
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| 196 | expectedModCount = modCount;
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| 197 | } catch (IndexOutOfBoundsException e) {
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| 198 | throw new ConcurrentModificationException();
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| 199 | }
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| 200 | }
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| 201 |
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| 202 | final void checkForComodification() {
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| 203 | if (modCount != expectedModCount)
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| 204 | throw new ConcurrentModificationException();
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| 205 | }
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| 206 | }
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| 207 |
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[1862] | 208 | }
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