/** Create a map from Integers -5 to -1 to Strings "A"-"E". */ private static ConcurrentNavigableMap dmap5() { ConcurrentSkipListMap map = new ConcurrentSkipListMap(); assertTrue(map.isEmpty()); map.put(m1, "A"); map.put(m5, "E"); map.put(m3, "C"); map.put(m2, "B"); map.put(m4, "D"); assertFalse(map.isEmpty()); assertEquals(5, map.size()); return map.descendingMap(); }