Serialize multiple different objects single in Java

Question

I might be trying to do this the hard way so let me know if there is a better solution.

I am making a simple text game in Java which you select your actions by a GUI. I have a couple of classes I am trying to serialize one being the player and another being an NPC. Is there an easy way to serialize more then one object (player and NPC) into the same file? I can serialize one object and load it back into the game.

Am I going about this the wrong way? Is there a simpler way of trying to save the game state?

If I have a class that creates multiple objects and I serialize that class, will the objects it created be serialized as well?

Thanks

Jason · Accepted Answer · 2016-08-11 00:01:25Z

3

An alternate approach to writing objects sequentially is to store them in a collection (e.g. a HashMap), since collections can be serialized. This may make it a little easier to manage upon retrieval, especially if you have many objects to serialize/deserialize. The following code demonstrates this:

    String first = "first";
    String second = "second";
    HashMap<String, Object> saved = new HashMap<String, Object>();
    saved.put("A", first);
    saved.put("B", second);

    try {
        FileOutputStream fos = new FileOutputStream("test.obj");
        ObjectOutputStream oos = new ObjectOutputStream(fos);
        oos.writeObject(saved);
        oos.flush();
        oos.close();
        fos.close();


        FileInputStream fis = new FileInputStream("test.obj");
        ObjectInputStream ois = new ObjectInputStream(fis);

        HashMap<String,Object> retreived = (HashMap<String,Object>)ois.readObject();
        fis.close();

        System.out.println(retreived.get("A"));
        System.out.println(retreived.get("B"));
    } catch (IOException e) {
        e.printStackTrace();
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    }
}

Running this should result in:

first
second

answered Aug 11, 2016 at 0:01

Jason

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2 Comments

jprogrammer Over a year ago

Thanks, this looks like it has worked. Instead of just printing out "A" and "B" into the console how as assign it back to an object I can do things with?

jprogrammer Over a year ago

I figured it out from here: stackoverflow.com/questions/7857935/… Thanks again for your answer it put me on the right track :)

user207421 · Accepted Answer · 2016-08-10 23:56:30Z

0

Just call writeObject() as many times with as many different objects as you need, and conversely call readObject() ditto.

Hard to believe you haven't already tried it.

answered Aug 10, 2016 at 23:56

user207421

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