return listIterator();
  }

  @Override
  public UnmodifiableListIterator<E> listIterator() {
    return listIterator(0);
  }

  @SuppressWarnings("unchecked")
  @Override
  public UnmodifiableListIterator<E> listIterator(int index) {
    checkPositionIndex(index, size());
    if (isEmpty()) {
      return (UnmodifiableListIterator<E>) EMPTY_ITR;
    } else {
      return new Itr<E>(this, index);