public class Main extends JavaPlugin implements Listener{

    private static Main instance;
    BukkitTask bt;
    Location arena = new Location(Bukkit.getWorlds().get(0), 100, 75, -100);
    private Map<String, String> map = new HashMap<String, String>();
    private Map<String, BukkitTask> task = new HashMap<String, BukkitTask>();

    @Override
    public void onEnable(){
        instance = this;
        System.out.println("Uruchamianie...");
        saveDefaultConfig();
        Bukkit.getPluginManager().registerEvents(this, this);
    }

    @Override
    public void onDisable(){
        System.out.println("Wylaczanie...");
    }

    public static Main getInst(){
        return instance;
    }

    public boolean onCommand(CommandSender sender, Command cmd, String label, String[] args){
        if(cmd.getName().equalsIgnoreCase("arena")){
            if(!(sender instanceof Player)){
                return true;
            }
            if(args.length < 1){
                return true;
            }
            if(Bukkit.getPlayer(args[0]) !=null){
                return true;
            }
            for(String s : map.keySet()){
                if(map.get(s).equalsIgnoreCase(args[0])){
                    if(Bukkit.getPlayer(s) !=null){
                        Bukkit.getPlayer(s).teleport(arena);
                        Bukkit.getPlayer(map.get(s)).teleport(arena);
                    } else{
                        sender.sendMessage("Ten gracz juz wyszedl!");
                    }
                    map.remove(s);
                    if(task.containsKey(s)){
                        task.remove(s).cancel();
                    }
                    return true;
                }
            }
            map.put(sender.getName(), args[0]);
            Bukkit.getPlayer(args[0]).sendMessage("Zostales zaproszony przez " + sender.getName());
            sender.sendMessage("Zaprosiles " + args[0]);
            bt = Bukkit.getScheduler().runTaskLater(this, new Runnable(){
                public void run(){
                    for(String s : task.keySet()){
                        if(task.get(s).equals(bt)){
                            task.remove(s);
                        }
                    }
                }
            }, 60*20);
            task.put(sender.getName(), bt);
            return true;
        }
        return false;
    }
}