code: public int size()
      {
          int count = 0;
  
          if (subMaps != null)
          {
              for (int i = 0; i < subMaps.length; i++)
              {
                  count += subMaps[i].size();
              }
          }
          return count;
      }
docs: This is a more performant implementation of this method than that
  found in AbstractMap. It simply iterates over the array of subMaps
  and adds together their sizes
  
  @return The number of elements in this ConcurrentHashMap