/** headMap returns map with keys in requested range */
  public void testTailMapContents() {
    ConcurrentNavigableMap map = map5();
    SortedMap sm = map.tailMap(two);
    assertFalse(sm.containsKey(one));
    assertTrue(sm.containsKey(two));
    assertTrue(sm.containsKey(three));
    assertTrue(sm.containsKey(four));
    assertTrue(sm.containsKey(five));
    Iterator i = sm.keySet().iterator();
    Object k;
    k = (Integer) (i.next());
    assertEquals(two, k);
    k = (Integer) (i.next());
    assertEquals(three, k);
    k = (Integer) (i.next());
    assertEquals(four, k);
    k = (Integer) (i.next());
    assertEquals(five, k);
    assertFalse(i.hasNext());

    Iterator ei = sm.entrySet().iterator();
    Map.Entry e;
    e = (Map.Entry) (ei.next());
    assertEquals(two, e.getKey());
    assertEquals("B", e.getValue());
    e = (Map.Entry) (ei.next());
    assertEquals(three, e.getKey());
    assertEquals("C", e.getValue());
    e = (Map.Entry) (ei.next());
    assertEquals(four, e.getKey());
    assertEquals("D", e.getValue());
    e = (Map.Entry) (ei.next());
    assertEquals(five, e.getKey());
    assertEquals("E", e.getValue());
    assertFalse(i.hasNext());

    SortedMap ssm = sm.tailMap(four);
    assertEquals(four, ssm.firstKey());
    assertEquals(five, ssm.lastKey());
    assertEquals("D", ssm.remove(four));
    assertEquals(1, ssm.size());
    assertEquals(3, sm.size());
    assertEquals(4, map.size());
  }
  /** headMap returns map with keys in requested range */
  public void testDescendingTailMapContents() {
    ConcurrentNavigableMap map = dmap5();
    SortedMap sm = map.tailMap(m2);
    assertFalse(sm.containsKey(m1));
    assertTrue(sm.containsKey(m2));
    assertTrue(sm.containsKey(m3));
    assertTrue(sm.containsKey(m4));
    assertTrue(sm.containsKey(m5));
    Iterator i = sm.keySet().iterator();
    Object k;
    k = (Integer) (i.next());
    assertEquals(m2, k);
    k = (Integer) (i.next());
    assertEquals(m3, k);
    k = (Integer) (i.next());
    assertEquals(m4, k);
    k = (Integer) (i.next());
    assertEquals(m5, k);
    assertFalse(i.hasNext());

    Iterator ei = sm.entrySet().iterator();
    Map.Entry e;
    e = (Map.Entry) (ei.next());
    assertEquals(m2, e.getKey());
    assertEquals("B", e.getValue());
    e = (Map.Entry) (ei.next());
    assertEquals(m3, e.getKey());
    assertEquals("C", e.getValue());
    e = (Map.Entry) (ei.next());
    assertEquals(m4, e.getKey());
    assertEquals("D", e.getValue());
    e = (Map.Entry) (ei.next());
    assertEquals(m5, e.getKey());
    assertEquals("E", e.getValue());
    assertFalse(i.hasNext());

    SortedMap ssm = sm.tailMap(m4);
    assertEquals(m4, ssm.firstKey());
    assertEquals(m5, ssm.lastKey());
    assertEquals("D", ssm.remove(m4));
    assertEquals(1, ssm.size());
    assertEquals(3, sm.size());
    assertEquals(4, map.size());
  }