尝试使用webdriver从excel中的单元格读取时获取空指针异常

Question

XSSFWorkbook wb = new XSSFWorkbook(fis);
XSSFSheet sheet =wb.getSheet("TestData");
           Row row = sheet.getRow(1);
           Cell cell = row.getCell(1);
           String x = "";
     x =cell.getStringCellValue();
     System.out.println(x);

我在Row row = sheet.getRow（1）;

获得NullPointerException