Question

I have a problem with the reference of a variable when loading a saved serialized object from a data file. All the variables referencing to the same object doesn’t seem to update on the change. I’ve made a code snipped below that illustrates the problem.

    Tournament test1 = new Tournament();
    Tournament test2 = test1;

    try {
        FileInputStream fis = new FileInputStream("test.out");
        ObjectInputStream in = new ObjectInputStream(fis);

        test1 = (Tournament) in.readObject();

        in.close();

    }
    catch (IOException ex){
        Logger.getLogger(Frame.class.getName()).log(Level.SEVERE, null, ex);
    }
    catch (ClassNotFoundException ex){
        Logger.getLogger(Frame.class.getName()).log(Level.SEVERE, null, ex);
    }

    System.out.println("test1: " + test1);
    System.out.println("test2: " + test2);

After this code is ran test1 and test2 doesn’t reference to the same object anymore. To my knowledge they should do that since in the declaration of test2 makes it a reference to test1. When test1 is updated test2 should reflect the change and return the new object when called in the code. Am I missing something essential here or have I been misstaught about how the variable references in Java works?

Answer 1

Am I missing something essential here
or have I been misstaught about how
the variable references in Java works?

Most likely you misunderstood what you were taught, or were taught something wrong. All variables of reference type (i.e. not primitive types) refer directly to an object.

Tournament test1 = new Tournament();

Creates a new instance of Tournament and makes test1 refer to it.

Tournament test2 = test1;

Copies the reference from test1 to test2, making them both refer to the same object.

test1 = (Tournament) in.readObject();

Makes test1 refer to a different object that has been deserialized from the stream, while test2 still refers to the original object.