poi读取数据怎么做非空判断和读取指定行

public ResponseResult uploading(MultipartFile file1) throws IOException {
    String filename = file1.getOriginalFilename();
    //        1.流读取文件
    FileInputStream stream = new FileInputStream("C:\\Users\\admin\\Desktop\\sss\\" + filename);

    //        2.通过poi解析流 得到 Excel文件对象
    HSSFWorkbook workbook = new HSSFWorkbook(stream);

    //        3.通过对象获取数据 得到表
    HSSFSheet sheet = workbook.getSheetAt(0 );

    HSSFRow  row=null;

     for(int i=0;sheet.getRow(i)!=null;i++){

        row=sheet.getRow(i);

     for(int j=0;row.getCell(j)!=null;j++){
    // System.out.print(row.getCell(j).toString()+"");
         if(j==1){
             System.out.print(row.getCell(0).getStringCellValue());
             System.out.println();
         }else if (j==2){
             System.out.print(row.getCell(2).getStringCellValue());
             System.out.println();
             }
          }
     }
    return ResponseResult.okMsg("提交成功");
}