save/load

//List<Arena> arenas;


private static File mainDir = Main.getDataFolder();
private static File arenas = new File(mainDir, "arenas");

public static void save(){
    for(Arena a:arenas){
        File f = new File(arenas, a.getId + ".yml");
        if(!f.exists()){
                try {
                    f.createNewFile();
                } catch (IOException e) {
                    e.printStackTrace();
                }
        }
        YamlConfiguration yml = YamlConfiguration.loadConfiguration(f);
        yml.set("id", a.getId());
        yml.set("firstx", a.locPlayer1().getX());
        yml.set("firsty", a.locPlayer1().getY());
        yml.set("firstz", a.locPlayer1().getZ());
        yml.set("scndx", a.locPlayer2().getX());
        yml.set("scndy", a.locPlayer2().getY());
        yml.set("scndz", a.locPlayer2().getZ());
        yml.set("name", a.getName()); //you should add this getter cause i cannot create an arena without that, and this string is set to private
        //it should NOT happen, but nobody knows...
        if(a.locPlayer1().getWorld().getName() == a.locPlayer2().getWorld().getName()){
            yml.set("world", a.locPlayer1().getWorld().getName());
        }
    }
}
public static void load(){
    for(File f:arenas.listFiles()){
        YamlConfiguration yml = YamlConfiguration.loadConfiguration(f);
        Arena a = new Arena(yml.getInt("id"), yml.getString("name"));
        for(World w: Bukkit.getWorlds()){
            if(w.getName() = yml.getString("world")){
                Location loc1 = new Location(w, yml.getDouble("firstx"), yml.getDouble("firsty"), yml.getDouble("firstz"));
                Location loc2 = new Location(w, yml.getDouble("scndx"), yml.getDouble("scndy"), yml.getDouble("scndz"));
                a.setPlayer1(loc1);
                a.setPlayer2(loc2);
            }
        }
        //again, it SHOULD be set, but it's just in case it would throw null;
        //make setter for name and ID
        a.setID(yml.getInt("id"));
        a.setName(yml.getString("name"));
    }
}