public void testAddAndRemove_concurrentHashMap() throws Exception {
    testAddAndRemove(new ConcurrentHashMap<String, AtomicInteger>());
  }

  public void testAddAndRemove_concurrentSkipListMap() throws Exception {
    testAddAndRemove(new ConcurrentSkipListMap<String, AtomicInteger>());
  }

  public void testAddAndRemove_mapMakerMap() throws Exception {
    MapMaker mapMaker = new MapMaker();