@Test public void testSubMap(){

    int nums[] = {1,2,3,4,5};
    ConcurrentNavigableMap m = new ConcurrentSkipListMap();
    for(int a:nums) for(int b:nums){
        m.put(t2(a,b),"");
    }
    assertEquals(5, m.subMap(t2(3, null), t2(3,HI)).size());
    assertEquals(3, m.subMap(t2(3, 3), t2(3,HI)).size());
    assertEquals(10, m.headMap(t2(3, null)).size());
    assertEquals(15, m.tailMap(t2(3, null)).size());
    assertEquals(10, m.headMap(t2(2, HI)).size());
    assertEquals(15, m.tailMap(t2(2, HI)).size());
}