code: @Override
    public void add(MtasDataItem<T1, T2> newItem) throws IOException {
      if (newItem instanceof MtasDataItemBasic) {
        MtasDataItemBasic<T1, T2> newTypedItem = (MtasDataItemBasic<T1, T2>) newItem;
        this.valueSum = operations.add11(this.valueSum, newTypedItem.valueSum);
        this.valueN += newTypedItem.valueN;
        recomputeComparableSortValue = true;
      } else {
        throw new IOException("can only add MtasDataItemBasic");
      }
    }
docs: /*
  (non-Javadoc)
  
  @see mtas.codec.util.DataCollector.MtasDataItem#add(mtas.codec.util.
  DataCollector.MtasDataItem)