if (delta >= 0) {
        multiset.add(key, delta);
      } else {
        multiset.remove(key, -delta);
      }
    }
    return blah;
  }

  private enum MultisetSupplier {
    CONCURRENT_HASH_MULTISET() {
      @Override
      Multiset<Integer> get() {
        return ConcurrentHashMultiset.create();
      }
    },
    BOXED_ATOMIC_REPLACE() {
      @Override
      Multiset<Integer> get() {