code: private void unmarshall()
      {
          sheetData = sheet.getJaxbElement().getSheetData();
          rows = sheetData.getRow();
          if(rows != null && rows.size() > 0)
          {
              Row r = (Row)rows.get(0);
              numColumns = r.getC().size();
          }
      }
docs: Unmarshall the data in this worksheet.