服务器上有几个人时，为什么调度程序无法正常工作

如何解决服务器上有几个人时，为什么调度程序无法正常工作

这是一个项目的代码，在该项目中，您只能在服务器上呆半天。它在单人游戏中可以正常工作，但是当服务器上有多个玩家时，调度程序将开始计数两次，并且一切都搞砸了。我希望有人能帮助我，我在这段代码中花了6个小时的工作，对此我感到沮丧。

package de.tombrenni.varo.listener;


import java.util.ArrayList;
import java.util.HashMap;

import org.bukkit.Bukkit;
import org.bukkit.ChatColor;
import org.bukkit.command.Command;
import org.bukkit.command.CommandExecutor;
import org.bukkit.command.CommandSender;
import org.bukkit.entity.Player;
import org.bukkit.event.EventHandler;
import org.bukkit.event.Listener;
import org.bukkit.event.player.PlayerJoinEvent;
import org.bukkit.event.player.PlayerQuitEvent;

import de.tombrenni.varo.main.Main;


public class OnlineCountdown implements Listener,CommandExecutor{

    private ArrayList<String> zählplayers = new ArrayList<>();
    private HashMap<Player,Integer> schedulers = new HashMap<>();
    private ArrayList<String> kickedplayers = new ArrayList<>();
    public int countdown = 180;
    public int countdown2 = countdown;
    public int countdown5;
    public int countdown6;
    
    @EventHandler
    public void handlePlayerjoin(PlayerJoinEvent event) {
Player player = event.getPlayer();
        
        event.setJoinMessage(null);
        
        
        
        if(!kickedplayers.contains(player.getName())) {
        Bukkit.broadcastMessage(ChatColor.GREEN + "Der Spieler " + ChatColor.RED + event.getPlayer().getName() + ChatColor.GREEN + " hat das Schlachtfeld" + ChatColor.GOLD +  " betreten");
        player.sendMessage(ChatColor.YELLOW + "Im Moment sind " + ChatColor.GREEN + ChatColor.BOLD + Bukkit.getOnlinePlayers().size() + ChatColor.YELLOW + " Feinde online");
        player.sendMessage(ChatColor.LIGHT_PURPLE + "Deine halbe Stunde läuft ab jetzt. Viel Glück");
        if(!zählplayers.contains(player.getName())) {
        zählplayers.add(player.getName());
        int taskID = Bukkit.getScheduler().scheduleSyncRepeatingTask(Main.getPlugin(),new Runnable() {
            
            
            
            @Override
              public void run() {
                countdown2 = countdown;
                  switch(countdown) {
                  case 900: case 600: case 300: case 120: case 60:
                      player.sendMessage(ChatColor.RED + "Deine Online-Zeit ist in " + ChatColor.AQUA + countdown /60 + ChatColor.RED + " Minuten um");
                      break;
                  case 30: case 15: case 10: case 5: case 4: case 3: case 2: case 1:
                     player.sendMessage(ChatColor.RED + "Deine Online-Zeit ist in " + ChatColor.AQUA + countdown + ChatColor.RED + " Sekunden um");
                      break;
                  case 0:
                      
                      player.kickPlayer(ChatColor.RED + "Deine Online Zeit ist vorbei");
                      kickedplayers.add(player.getName());
                      Bukkit.getScheduler().cancelTask(schedulers.remove(player));
                      return;

                      default: 
                          break;
                  }
                  countdown --;

              }

          },20);
        schedulers.put(player,taskID);
        } else {
        
            player.sendMessage(ChatColor.RED + "Deine Zeit läuft noch. Du hast noch " + ChatColor.AQUA + countdown + ChatColor.RED + " Sekunden übrig");
        int taskID = Bukkit.getScheduler().scheduleSyncRepeatingTask(Main.getPlugin(),new Runnable() {
            
            
            
            @Override
              public void run() {
                
                  switch(countdown) {
                  case 900: case 600: case 300: case 120: case 60:
                      player.sendMessage(ChatColor.RED + "Deine Online-Zeit ist in " + ChatColor.AQUA + countdown /60 + ChatColor.RED + " Minuten um");
                      break;
                  case 30: case 15: case 10: case 5: case 4: case 3: case 2: case 1:
                     player.sendMessage(ChatColor.RED + "Deine Online-Zeit ist in " + ChatColor.AQUA + countdown + ChatColor.RED + " Sekunden um");
                      break;
                  case 0:
                      kickedplayers.add(player.getName());
                      player.kickPlayer(ChatColor.RED + "Deine Online Zeit ist vorbei");
                      Bukkit.getScheduler().cancelTask(schedulers.remove(player));
                      return;

                      default: 
                          break;
                  }
                  countdown --;
                  

              }

          },taskID);
        }
        }else 
            player.kickPlayer(ChatColor.RED + "Du warst heute schon mal online");
}       
    @EventHandler
    public void handlePlayerquit(PlayerQuitEvent event) {
        Player player = event.getPlayer();
        Bukkit.broadcastMessage(ChatColor.GREEN + "Der Spieler " + ChatColor.RED + event.getPlayer().getName() + ChatColor.GREEN + " hat das Schlachtfeld" + ChatColor.GOLD +  " verlassen");
        Bukkit.getScheduler().cancelTask(schedulers.remove(player));
        if(!kickedplayers.contains(player.getName())) {

            
            
        }else
            return;
            
    }
    public boolean onCommand(CommandSender sender,Command command,String label,String[] args) {
        if(sender instanceof Player) {
            Player player = (Player) sender;
            if(args.length == 0) {
            if(countdown <= 60) {
                
                player.sendMessage(ChatColor.DARK_GREEN + "Du hast noch " + countdown + " Sekunden Online-Zeit");
                
            } else {
                countdown5 = countdown / 60;
                countdown6 = Math.round(10 * countdown5) / 10;
                player.sendMessage(ChatColor.DARK_GREEN + "Du hast noch ungefähr " + countdown6 + " Minuten Online-Zeit");
            }
                
            }else
                
            player.sendMessage(ChatColor.DARK_RED + "Bitte benutze " + ChatColor.GOLD + "/time");
        } else
            
        sender.sendMessage(ChatColor.DARK_RED + "Diesen Command kannst du nur als Spieler im Chatfenster benutzen");
        
        return false;
    }
            
            
}