/** lowerEntry returns preceding entry. */
  public void testDescendingLowerEntry() {
    ConcurrentNavigableMap map = dmap5();
    Map.Entry e1 = map.lowerEntry(m3);
    assertEquals(m2, e1.getKey());

    Map.Entry e2 = map.lowerEntry(m6);
    assertEquals(m5, e2.getKey());

    Map.Entry e3 = map.lowerEntry(m1);
    assertNull(e3);

    Map.Entry e4 = map.lowerEntry(zero);
    assertNull(e4);
  }
  /** lowerEntry returns preceding entry. */
  public void testLowerEntry() {
    ConcurrentNavigableMap map = map5();
    Map.Entry e1 = map.lowerEntry(three);
    assertEquals(two, e1.getKey());

    Map.Entry e2 = map.lowerEntry(six);
    assertEquals(five, e2.getKey());

    Map.Entry e3 = map.lowerEntry(one);
    assertNull(e3);

    Map.Entry e4 = map.lowerEntry(zero);
    assertNull(e4);
  }