}
    },
    BOXED_ATOMIC_REPLACE() {
      @Override
      Multiset<Integer> get() {
        return OldConcurrentHashMultiset.create();
      }
    },
    SYNCHRONIZED_MULTISET() {
      @Override
      Multiset<Integer> get() {
        return Synchronized.multiset(HashMultiset.<Integer>create(), null);
      }
    },
    ;

    abstract Multiset<Integer> get();
  }