// Textbook fragment 06.14
public class ElementIterator<E> implements Iterator<E> {
  protected PositionList<E> list; // the underlying list
  protected Position<E> cursor; // the next position
  /** Creates an element iterator over the given list. */
  public ElementIterator(PositionList<E> L) {
    list = L;
    cursor = (list.isEmpty())? null : list.first();
  }
  public boolean hasNext() { return (cursor != null);  }
  public E next() throws NoSuchElementException {
    if (cursor == null)
      throw new NoSuchElementException("No next element");
    E toReturn = cursor.element();
    cursor = (cursor == list.last())? null : list.next(cursor);
    return toReturn;
  }
}