code: public void update(final T dataItem) {
      if (dataItem == null) { return; }
      if (gadget_ == null) {
        gadget_ = ItemsSketch.getInstance(maxK_, comparator_);
      }
      gadget_.update(dataItem);
    }
docs: Update this union with the given double (or float) data Item.
  
  @param dataItem The given datum.