code: @Override
    public void add(MtasDataItem<T1, T2> newItem) throws IOException {
      if (newItem instanceof MtasDataItemAdvanced) {
        MtasDataItemAdvanced<T1, T2> newTypedItem = (MtasDataItemAdvanced<T1, T2>) newItem;
        valueSum = operations.add11(valueSum, newTypedItem.valueSum);
        valueSumOfLogs = operations.add22(valueSumOfLogs,
            newTypedItem.valueSumOfLogs);
        valueSumOfSquares = operations.add11(valueSumOfSquares,
            newTypedItem.valueSumOfSquares);
        valueMin = operations.min11(valueMin, newTypedItem.valueMin);
        valueMax = operations.max11(valueMax, newTypedItem.valueMax);
        valueN += newTypedItem.valueN;
        recomputeComparableSortValue = true;
      } else {
        throw new IOException("can only add MtasDataItemAdvanced");
      }
    }
docs: /*
  (non-Javadoc)
  
  @see mtas.codec.util.DataCollector.MtasDataItem#add(mtas.codec.util.
  DataCollector.MtasDataItem)