Iterator<Row> sheetRowIterator;
List<String> stringCache;
private HSSFRowSource(HSSFWorkbook workbook) {
this.workbook = workbook;
this.formatter = new HSSFDataFormatter();
this.evaluator = new HSSFFormulaEvaluator(workbook);
this.stringCache = new ArrayList<String>();
initSheetIterator(workbook.getSheetAt(0));
}