public final String finishRow() 
{
        int listindex = ((List) getDecoratedObject()).indexOf(this.getCurrentRowObject());
        ReportableListObject reportableObject = (ReportableListObject) this.getCurrentRowObject();
        String nextCity = null;
        this.cityTotal += reportableObject.getAmount();
        this.grandTotal += reportableObject.getAmount();
        if (listindex != ((List) getDecoratedObject()).size() - 1)
        {
            nextCity = ((ReportableListObject) ((List) getDecoratedObject()).get(listindex + 1)).getCity();
        }
        this.buffer = new StringBuffer(1000);
        // City subtotals...
        if (!ObjectUtils.equals(nextCity, reportableObject.getCity()))
        {
            writeCityTotal(reportableObject.getCity(), this.cityTotal);
            this.cityTotal = 0;
        }
        // Grand totals...
        if (getViewIndex() == ((List) getDecoratedObject()).size() - 1)
        {
            writeGrandTotal(this.grandTotal);
        }
        return buffer.toString();
}

After every row completes we evaluate to see if we should be drawing a new total line and summing the results from the previous group.

 protected StringBuffer getStringBuffer() 
{
        return this.buffer;
}

Obtain the StringBuffer used to build the totals line.

 abstract protected  void writeCityTotal(String city,
    double total)
Render the city total in the appropriate format.

 abstract protected  void writeGrandTotal(double total)
Render the grand total in the appropriate format.