通過該工具類，讀取cell的時候不會報錯。不管是數字還是String，或者null值，都是可以讀取。不會報錯！

   public static String getStringValueFromCell(Cell cell) {
        SimpleDateFormat sFormat = new SimpleDateFormat("MM/dd/yyyy");
        DecimalFormat decimalFormat = new DecimalFormat("#.#");
        String cellValue = "";
        if(cell == null) {
            return cellValue;
        }
        else if(cell.getCellType() == Cell.CELL_TYPE_STRING) {
            cellValue = cell.getStringCellValue();
        }

        else if(cell.getCellType() == XSSFCell.CELL_TYPE_NUMERIC) {
            if(HSSFDateUtil.isCellDateFormatted(cell)) {
                double d = cell.getNumericCellValue();
                Date date = HSSFDateUtil.getJavaDate(d);
                cellValue = sFormat.format(date);
            }
            else {                
                cellValue = decimalFormat.format((cell.getNumericCellValue()));
            }
        }
        else if(cell.getCellType() == Cell.CELL_TYPE_BLANK) {
            cellValue = "";
        }
        else if(cell.getCellType() == Cell.CELL_TYPE_BOOLEAN) {
            cellValue = String.valueOf(cell.getBooleanCellValue());
        }
        else if(cell.getCellType() == Cell.CELL_TYPE_ERROR) {
            cellValue = "";
        }
        else if(cell.getCellType() == Cell.CELL_TYPE_FORMULA) {
            cellValue = cell.getCellFormula().toString();
        }
        return cellValue;
    }