@LazyInit @CheckForNull private transient Integer size;

    @Override
    public int size() {
      // racy single-check idiom
      Integer result = size;
      if (result == null) {
        long total = 0;
        for (Range<C> range : ranges) {
          total += ContiguousSet.create(range, domain).size();
          if (total >= Integer.MAX_VALUE) {
            break;
          }
        }