Countdown.java

// Coundown class by @CeramicTitan / @ZeusAllMighty11, modified by GameplayJDK
package de.GameplayJDK.Lib.Util.Runnables;

import org.bukkit.plugin.Plugin;
import org.bukkit.scheduler.BukkitRunnable;
import org.bukkit.scheduler.BukkitTask;

public class Countdown {
    // ==================================================================== \\

    public interface CountdownHandler {
	public void onStart();
	public void onFinish();
	public void onTick(int tick);
    }

    // ==================================================================== \\
    Plugin plugin; // the main class which extends JavaPlugin
    int time;	// how long the countdown will run for(In Seconds).
    BukkitTask task;	// task variable
    CountdownHandler handler; // handler interface implemented
    boolean finished; // if the countdown is finished

    // ==================================================================== \\

    /**
     * @param plugin - Replace Goblet with the name of your class that extends JavaPlugin
     * @param length - How long the plugin will run for
     */
    public Countdown(Plugin plugin, int length)
    {
	this.plugin = plugin;
	this.time = length;
    }

    // ==================================================================== \\

    public void start() {
	// lets all implementing interfaces know it started
	handler.onStart();

	// schedule runnable
	task = new BukkitRunnable() {
	    @Override
	    public void run() {
		if(time <1) {
		    finished = true;
		    handler.onFinish();
		    task.cancel();
		    return;
		}
		handler.onTick(time); // give the current time (in Seconds) to the onTick method to allow operations depending on time
		time--;
	    }
	}.runTaskTimer(plugin, 0L, 20L);// Start without delay (0L), Repeat every 20 ticks (ca. 1s)
					// This method depends on how many tps the server has, which may differ.
					// The more exact method is to use runTaskTimerAsychronously (which is executed in an seperate thread) instead of runTaskTimer (which is executed by the main server thread like everything else)
    }

    public void stop() {
	task.cancel();
    }

    public boolean isFinished() {
	return finished;
    }

    // ==================================================================== \\
    /*
     *
     * When you declare your countdown variable, use the setHandler method 
     * so your plugin can "listen" to the onStart, onTick, and onFinish "events"
     * 
     */

    public void setHandler(CountdownHandler handler) {
	this.handler=handler;
    }

    // ==================================================================== \\
}