Question

To save teleportation points on command, I have an HashMap:

public HashMap<Player, Location> mapHomes = new HashMap<>();

Which is accessed like this:

if(cmd.getName().equalsIgnoreCase("sethome")){
    Location loc = player.getLocation();
    mapHomes.put(player, loc);
    sender.sendMessage("Home set !");
    return true;
}
if(cmd.getName().equalsIgnoreCase("home")){
    Location loc1 = mapHomes.get(player);
    player.teleport(loc1);
    sender.sendMessage("Teleported to home");
    return true;
}
return false;

Since these settings should be kept on restart, I’ve implemented a save method:

public void save(HashMap<Player,Location> mapHome, String path) throws NotSerializableException{
    try{
        ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(path));
        oos.writeObject(mapHome);
        oos.flush();
        oos.close();
    }catch(Exception e){
        e.printStackTrace();
    }
}

But it’s not working. It throws NotSerializableException.

I think the main problem is Player and Location are not serializable types, so what should I do to write this HashMap?

Answer 1

HashMap is already Serializable.

The problem is that the objects inside the map are not, so you’ll have to make them serializable, too.

public class SerializedPlayer extends Player implements Serializable {
    public SerializedPlayer() {}
    public SerializedPlayer(Player playerToClone) {
        this.setField1(playerToClone.getField1());
        // Set all the fields
    }
}

When adding to the map:

map.put(new SerializedPlayer(player), new SerializedLocation(location));