public Iterator<E> iterator() { return new Itr(); }
private class Itr implements Iterator<E> { int cursor; int lastRet = -1; // 复制集合的修改次数并保存 int expectedModCount = modCount;
Itr() {}
public boolean hasNext() { return cursor != size; }
@SuppressWarnings("unchecked") public E next() { // 快速失败的核心代码 checkForComodification(); int i = cursor; if (i >= size) throw new NoSuchElementException(); Object[] elementData = ArrayList.this.elementData; if (i >= elementData.length) throw new ConcurrentModificationException(); cursor = i + 1; return (E) elementData[lastRet = i]; }
public void remove() { if (lastRet < 0) throw new IllegalStateException(); checkForComodification();
@Override @SuppressWarnings("unchecked") public void forEachRemaining(Consumer<? super E> consumer) { Objects.requireNonNull(consumer); final int size = ArrayList.this.size; int i = cursor; if (i >= size) { return; } final Object[] elementData = ArrayList.this.elementData; if (i >= elementData.length) { throw new ConcurrentModificationException(); } while (i != size && modCount == expectedModCount) { consumer.accept((E) elementData[i++]); } // update once at end of iteration to reduce heap write traffic cursor = i; lastRet = i - 1; checkForComodification(); }
final void checkForComodification() { // 如果集合的修改次数不等于迭代器创建时,则抛出并发修改异常 if (modCount != expectedModCount) throw new ConcurrentModificationException(); } }
@Override public void forEach(Consumer<? super E> action) { Objects.requireNonNull(action); final int expectedModCount = modCount; @SuppressWarnings("unchecked") final E[] elementData = (E[]) this.elementData; final int size = this.size; for (int i=0; modCount == expectedModCount && i < size; i++) { action.accept(elementData[i]); } if (modCount != expectedModCount) { throw new ConcurrentModificationException(); } }