回答編集履歴
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追記
test
CHANGED
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@@ -11,3 +11,141 @@
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この例外は、オブジェクトの並行変更を検出したメソッドによって、そのような変更が許可されていない場合にスローされます。
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```
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### ArrayList$Itr の実装
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```
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private class Itr implements Iterator<E> {
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int cursor; // index of next element to return
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int lastRet = -1; // index of last element returned; -1 if no such
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int expectedModCount = modCount;
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// prevent creating a synthetic constructor
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Itr() {}
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public boolean hasNext() {
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return cursor != size;
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}
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@SuppressWarnings("unchecked")
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public E next() {
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checkForComodification();
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int i = cursor;
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if (i >= size)
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throw new NoSuchElementException();
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Object[] elementData = ArrayList.this.elementData;
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if (i >= elementData.length)
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throw new ConcurrentModificationException();
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cursor = i + 1;
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return (E) elementData[lastRet = i];
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}
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public void remove() {
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if (lastRet < 0)
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throw new IllegalStateException();
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checkForComodification();
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try {
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ArrayList.this.remove(lastRet);
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cursor = lastRet;
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lastRet = -1;
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expectedModCount = modCount;
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} catch (IndexOutOfBoundsException ex) {
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throw new ConcurrentModificationException();
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}
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}
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@Override
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public void forEachRemaining(Consumer<? super E> action) {
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Objects.requireNonNull(action);
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final int size = ArrayList.this.size;
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int i = cursor;
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if (i < size) {
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final Object[] es = elementData;
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if (i >= es.length)
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throw new ConcurrentModificationException();
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for (; i < size && modCount == expectedModCount; i++)
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action.accept(elementAt(es, i));
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// update once at end to reduce heap write traffic
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cursor = i;
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lastRet = i - 1;
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checkForComodification();
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}
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}
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final void checkForComodification() {
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if (modCount != expectedModCount)
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throw new ConcurrentModificationException();
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}
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}
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```
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つまり Iterator が作成されたときと 処理を実行したときに違いがあればエラーとなる。
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