@Override
  public T peekLast()
  {
    if (_tail == null)
    {
      return null;
    }
    return _tail._value;
  }
@Test
  public void testPeekLast()
  {
    List<Integer> control = new ArrayList<>(Arrays.asList(1, 2, 3));
    LinkedDeque<Integer> q = new LinkedDeque<>(control);

    Assert.assertEquals(q.peekLast(), control.get(control.size() - 1));
    Assert.assertEquals(q, control);
  }