反序列化具有多个对象的 ArrayList

Question

I have stored multiple objects in Teacher ArrayList and I'm trying to deserialize it, but it shows the garbage value.

public void Write(){
    try{
        FileOutputStream fs=new FileOutputStream("S.txt");
        ObjectOutputStream os=new ObjectOutputStream(fs);
        os.writeObject(teachers);

        os.close();
    }catch(Exception e)
    {System.out.println(e);}

}


public void Read(){
    try
    {
        FileInputStream fis = new FileInputStream("E:\\Books\\OOP\\Teacher\\S.txt");
        ObjectInputStream ois = new ObjectInputStream(fis);
        teachers = (ArrayList<Teacher>) ois.readObject();
        for(Teacher i: teachers){
            System.out.println(i.toString());
        }
        ois.close();
        fis.close();
    }catch(IOException ioe){
        System.out.println("Error");
        return;
    }catch(ClassNotFoundException c){
        System.out.println("Class not found");

        return;
    }
}

Answer 1

You are using object streams, which persist your serialized objects in binary, regardless of the extension of the file (which happens to be ".txt" here, ambiguously suggesting that it'll be a text file when written).

You cannot view anything human-like from your file with a text editor when the data written is binary data.

If your "garbage values" also get printed when you iterate your List<Teacher> upon de-serialization, it implies that:

1. (De-)serialization actually succeeded (ie you've written your List<Teacher> to file and retrieved it)
2. Your Teacher class might not override toString properly or at all, so it prints the Type@hashCode notation from Object#toString when fed to the system output print stream