CountdownPlugin

package com.acuddlyheadcrab.testplugin;

import java.util.Random;

import org.bukkit.Bukkit;
import org.bukkit.event.Listener;
import org.bukkit.plugin.java.JavaPlugin;

public class TestPlugin extends JavaPlugin implements Listener{

    public TestPlugin plugin = this;

    private int countdown_secs = 0; //hehe secs... sex

    public void onEnable() {
        /* this is just used to  get a random number between 3 and 13 for demonstration
        +3 so that we don't have 0 for the countdown */
        int rand_seconds = new Random().nextInt(7)+3;

        System.out.println("Starting countdown");
        startCountdown(rand_seconds);
    }

    public void onDisable() {}

    public void startCountdown(final int seconds){
        long increment = 20; // just so you know, 1 tick == 1/20 second
        countdown_secs = seconds;

        Bukkit.getScheduler().scheduleSyncRepeatingTask(this, new Runnable() {
            @Override
            public void run() {


//              this is where you check if the countdown is done yet
                if(countdown_secs<1){
                    Bukkit.getScheduler().cancelTasks(plugin);
                    System.out.println("Boom! Countdown is done!!");
                }

                displayCountdown();

                countdown_secs--;

            }
        }, increment, increment);


    }

    public void displayCountdown() {
        // put however you want to display the countdown info here
        int seconds = countdown_secs;
        System.out.println("Countdown: "+seconds);
    }
}