code: @Override
    public int size() {
      long sum = 0L;
      for (AtomicInteger value : countMap.values()) {
        sum += value.get();
      }
      return Ints.saturatedCast(sum);
    }
docs: {@inheritDoc}
  
  <p>If the data in the multiset is modified by any other threads during this method, it is
  undefined which (if any) of these modifications will be reflected in the result.