}

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