code: public E peekLast() {
          final Node<E> l = last;
          return (l == null) ? null : l.item;
      }
docs: Retrieves, but does not remove, the last element of this list,
  or returns {@code null} if this list is empty.
  
  @return the last element of this list, or {@code null}
  if this list is empty
  @since 1.6