Timer

package io.github.penguinhi5.timer;

import org.bukkit.Bukkit;
import org.bukkit.ChatColor;
import org.bukkit.command.Command;
import org.bukkit.command.CommandSender;
import org.bukkit.entity.Player;
import org.bukkit.plugin.java.JavaPlugin;
import org.bukkit.scoreboard.DisplaySlot;
import org.bukkit.scoreboard.Objective;
import org.bukkit.scoreboard.Score;
import org.bukkit.scoreboard.Scoreboard;
import org.bukkit.scoreboard.ScoreboardManager;

public final class Timer extends JavaPlugin {
    public void onEnable() {
        getLogger().info("onEnable has been invoked!");
    }

    public void onDisable() {
        getLogger().info("onDisable has been invoked!");
    }
    public boolean onCommand(CommandSender sender, Command cmd, String label, String[] args) {
        if (cmd.getName().equalsIgnoreCase("timer")) {
            Bukkit.getScheduler().runTaskTimer(this, new Runnable() {
                int seconds = 30;

                public void run() {
                ScoreboardManager manager = Bukkit.getScoreboardManager();
                Scoreboard timer = manager.getNewScoreboard();
                Objective objective = timer.registerNewObjective("timer", "dummy");
                objective.setDisplaySlot(DisplaySlot.SIDEBAR);
                objective.setDisplayName(ChatColor.GREEN + "" + ChatColor.BOLD + "Timer");
                Score space = objective.getScore("");
                space.setScore(2);
                Score time = objective.getScore(ChatColor.GREEN + "" + ChatColor.BOLD + "Starting in " + ChatColor.BLUE + seconds + ChatColor.GREEN + " Seconds");
                time.setScore(1);

                if (seconds == 0){
                    Bukkit.getServer().getScheduler().cancelAllTasks();
                    Bukkit.broadcastMessage(ChatColor.RED + "" + ChatColor.BOLD + "The timer has ended!");
                } else {
                    seconds--;
                }

                for (Player online : Bukkit.getOnlinePlayers()) {
                    online.setScoreboard(timer);
                }
                }
            }, 0L, 20L);

            return true;
        }
        return false;
    }
}