for (int i = 0; i <= lastRowNum+1; i++) {
    HSSFRow row = sheet.getRow(i);
    // 获取列数
    int lastCellNum = row.getLastCellNum();
    System.out.println("列数是："+lastCellNum);
    for (int j = 0; j <= lastCellNum+1; j++) {
     
     HSSFCell cell = row.getCell(j);
     String value = null;
     if ((value=cell.getStringCellValue())!=null) {
      System.out.print(value + "  ");
     }
     else {
      continue;
     }
    }
    System.out.println("写出成功！");
   }

你好，这是我写的代码，在cell.getStringCellValue();处也会报空指针异常，请问循环有什么错误呢