Solved PotionEffect doesn't work

Hey guys, so as the title says i don't know why but when i coded a plugin that gives the player potion effect(absorption) it throws an exception in my server's console :

Code:

2:55:41] [Craft Scheduler Thread - 0/WARN]: Exception in thread "Craft Scheduler Thread - 0"
[12:55:41] [Craft Scheduler Thread - 0/WARN]: org.apache.commons.lang.UnhandledException: Plugin 8omidha v1.0 generated an exception while executing task 2
    at org.bukkit.craftbukkit.v1_10_R1.scheduler.CraftAsyncTask.run(CraftAsyncTask.java:56)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.IllegalStateException: Asynchronous effect add!
    at org.spigotmc.AsyncCatcher.catchOp(AsyncCatcher.java:14)
    at net.minecraft.server.v1_10_R1.EntityLiving.addEffect(EntityLiving.java:648)
    at org.bukkit.craftbukkit.v1_10_R1.entity.CraftLivingEntity.addPotionEffect(CraftLivingEntity.java:300)
    at org.bukkit.craftbukkit.v1_10_R1.entity.CraftLivingEntity.addPotionEffect(CraftLivingEntity.java:290)
    at com.night.Game.StartGame(Game.java:135)
    at com.night.Game$1.run(Game.java:114)
    at org.bukkit.craftbukkit.v1_10_R1.scheduler.CraftTask.run(CraftTask.java:71)
    at org.bukkit.craftbukkit.v1_10_R1.scheduler.CraftAsyncTask.run(CraftAsyncTask.java:53)
    ... 3 more

and this is my code :

Code:

@SuppressWarnings("deprecation")
    public boolean onCommand(CommandSender sender, Command command, String label, String[] args) {
        if (!(sender instanceof Player))
            return false;
        Player player = (Player) sender;
        if (label.equalsIgnoreCase("Start")) {                       
            player.sendMessage(ChatColor.GREEN + "You've started the Countdown !!");

    Bukkit.getScheduler().scheduleAsyncRepeatingTask(this, new Runnable(){
   
                public void run(){
                    if (CountDown >= 0) {
                        for (Player p : Bukkit.getOnlinePlayers()) {
                            p.playSound(p.getLocation(), Sound.ENTITY_EXPERIENCE_ORB_PICKUP, 10f, 10f);
                            CountDown--;
                           
                        }
                           
                       
                    } else if (CountDown == -1) {
                        for (Player p : Bukkit.getOnlinePlayers()) {
                            p.playSound(p.getLocation(), Sound.ENTITY_PLAYER_LEVELUP, 10f, 10f);
                            p.sendMessage(ChatColor.GREEN + "The Game Has Started");
                            CountDown --;
                            StartGame();
                           
                        }
                       
                   
                }

                }
            }, 0L, 20L);
        }
        return true;
    }

    public void StartGame(){
        Hiders hiders = new Hiders(this);
        Seekers seekers = new Seekers(this);
       
        for (Player player : Bukkit.getOnlinePlayers()){

            if(hiders.getAllPlayers().contains(player)){
                player.sendMessage(ChatColor.GOLD + "Test 1");
                player.addPotionEffect(new PotionEffect(PotionEffectType.ABSORPTION,10,10,false));
           
           
            }else if(seekers.getAllPlayers().contains(player)){
                player.sendMessage("Test 2 ");
            }
        }
        Bukkit.getServer().broadcastMessage(ChatColor.GREEN + "TEST");
   
        GameStarted = true;
    }

 

@nightwolf111
The problem is that the task is asyncronous. I have to ask, is there a reason for it to be asynchronous? Because if there isn't you could just switch it to a synchronous task and that'd fix you problem.

 

thanx it worked fine ^^, but can you explain to me why it threw the exception when i make sychronized task ? what does that mean ?