public void incrCounter(Enum<?> key, long amount) {
    findCounter(key).increment(amount);
  }
@SuppressWarnings("deprecation")
  @Test
  public void testCounterIteratorConcurrency() {
    Counters counters = new Counters();
    counters.incrCounter("group1", "counter1", 1);
    Iterator<Group> iterator = counters.iterator();
    counters.incrCounter("group2", "counter2", 1);
    iterator.next();
  }