// Textbook fragment 05.18
  public E removeLast() throws EmptyDequeException {
    if (isEmpty())
      throw new EmptyDequeException("Deque is empty.");
    DLNode<E> last = trailer.getPrev();
    E o = last.getElement();
    DLNode<E> secondtolast = last.getPrev();
    trailer.setPrev(secondtolast);
    secondtolast.setNext(trailer);
    size--;
    return o;
  }