android/guava/src/com/google/common/collect/ConcurrentHashMultiset.java
@Override
  public int size() {
    long sum = 0L;
    for (AtomicInteger value : countMap.values()) {
      sum += value.get();
    }
    return Ints.saturatedCast(sum);
  }
@Override
  public int size() {
    long sum = 0L;
    for (AtomicInteger value : countMap.values()) {
      sum += value.get();
    }
    return Ints.saturatedCast(sum);
  }
{@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.