File aFile=new File("e:\\c.txt");
    Stu a=new Stu(1, "aa", "1");
    FileOutputStream fileOutputStream=null;
    try {
      fileOutputStream = new FileOutputStream(aFile);
      ObjectOutputStream objectOutputStream=new ObjectOutputStream(fileOutputStream);
      objectOutputStream.writeObject(a);
      objectOutputStream.flush();
      objectOutputStream.close();
    } catch (FileNotFoundException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    } catch (IOException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    }finally {
      if(fileOutputStream!=null)
      {
        try {
          fileOutputStream.close();
        } catch (IOException e) {
          // TODO Auto-generated catch block
          e.printStackTrace();
        }      
      }
    }

FileInputStream fileInputStream=new FileInputStream(aFile);
ObjectInputStream objectInputStream=new ObjectInputStream(fileInputStream);
Stu s=(Stu)objectInputStream.readObject();
System.out.println(s);