/** Maps with same contents are equal */
 public void testEquals() {
   ConcurrentNavigableMap map1 = map5();
   ConcurrentNavigableMap map2 = map5();
   assertEquals(map1, map2);
   assertEquals(map2, map1);
   map1.clear();
   assertFalse(map1.equals(map2));
   assertFalse(map2.equals(map1));
 }
 /** clear removes all pairs */
 public void testClear() {
   ConcurrentNavigableMap map = map5();
   map.clear();
   assertEquals(map.size(), 0);
 }