Saving and loading an Arraylist of classes via ObjectInputStream

Question

I'm currently trying to save and load multiple instances of a class of type 'Player' via serialization. (This is for an assignment as an fyi).

The way the process currently works is I run the class via an ObjectOutputStream.writeObject(Player), this seems to work as I get the text file with what appears to be class data.

The problem I'm currently having is when I reverse and load the class, I'm unable to cast the object back to a player object, it is throwing an exception, however I'm not currently knowledgeable enough to figure out the exact exception.

Please find below the functions.

Save function:

public void savePlayers(ArrayList<Player> p)
{
    FileOutputStream fout = null;
    ObjectOutputStream oos = null;
    try
    {
        fout = new FileOutputStream("Player.txt");
        oos = new ObjectOutputStream(fout);
        for(Player player: p)
        {
          oos.writeObject(p);
        }
        fout.close();
        oos.close();
      }

    catch(Exception e)
    {
        System.out.println("Error is: " + e);
    }
    finally
    {
        closeStreams(fout, oos);
    }

}

Load Function:

public ArrayList<Player> loadPlayers() 
{   

    ArrayList<Player> loadedList = new ArrayList<Player>();

    FileInputStream fis;
    ObjectInputStream ois;

    try
    {
        fis = new FileInputStream("Player.txt");
        ois = new ObjectInputStream(fis);

       while(true)
       {
           System.out.println("Entered loop"); //testing
           Object obj = ois.readObject();
           System.out.println("Read object done"); //testing
           Player p = (Player)obj;
           System.out.println("Casted player"); //The line here doesn't run, prints out error from exception instead and exits loop
           loadedList.add(p);
           System.out.println("Loop iterated");
       }
    }
    catch(EOFException eof)
    {

    }
    catch(Exception e)
    {
           System.out.println("Exception here");
    }
}

Is there a better way to save the classes? Am I doing something wrong when casting?

why won't you print the actual error message and see what it says? — Nir Alfasi
– Nir Alfasi, Commented Oct 17, 2017 at 2:07
How is Player defined? Also do not silently swallow exceptions — Scary Wombat
– Scary Wombat, Commented Oct 17, 2017 at 2:10
Whoops! Teacher had typed that to see where the error was coming from and I forgot to change it, it comes with: java.io.WriteAbortedException: writing aborted; java.io.NotSerializableException: australianopen.GameController. Going to have to scour through that class and figure out what's going on — AidanJH
– AidanJH, Commented Oct 17, 2017 at 2:13
Player is defined in its own class, it implements serializable, the arraylist containing players is contained in another class, and then that arraylist is passed through the function as above. — AidanJH
– AidanJH, Commented Oct 17, 2017 at 2:18

Scary Wombat · Accepted Answer · 2017-10-17 02:11:56Z

2

change to

oos.writeObject(player);

and the moment you are writing the whole ArrayList multiple times

answered Oct 17, 2017 at 2:11

Scary Wombat

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1 Comment

AidanJH Over a year ago

Thanks! I'm now not getting exceptions or errors, hopefully I can fix the rest of the spaghetti and finally get some players loaded!

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