Bukkit Runnables and Properly Shutting Down

I'm relatively new to Java, so excuse my ignorance.

I have found using BukkitRunnables is must easier than BukkitSchedulers. But when I use them, I get the seemingly common error "This plugin is not properly shutting down its async tasks when it is being reloaded. This may cause conflicts with the newly loaded version of the plugin" from many of the other plugins on the server, when I reload the server.

I'm not really sure what causes this, whether it be because I'm not assigning taskIDs or something. And I can't seem to find any problems that are a result of this, but it's the knowing that kills me.

Code:

package askyra.clans;

import org.bukkit.event.EventHandler;
import org.bukkit.event.Listener;
import org.bukkit.event.player.PlayerCommandPreprocessEvent;
import org.bukkit.plugin.java.JavaPlugin;
import org.bukkit.scheduler.BukkitRunnable;

public final class Main extends JavaPlugin {

    @Override
    public void onEnable() {
        new ExampleListener(this);
    }
}

class ExampleListener implements Listener {

    private final Main plugin;

    public ExampleListener(Main plugin) {
        this.plugin = plugin;
        this.plugin.getServer().getPluginManager().registerEvents(this, plugin);
    }

    @EventHandler
    public void onJoin(PlayerJoinEvent event) {
        new BukkitRunnable() {

            @Override
            public void run() {
                plugin.getServer().broadcastMessage("Welcome to Bukkit! Remember to read the documentation!");
            }

        }.runTaskLater(this.plugin, 20);
    }

}

I literally copied this code right from Bukkit's "Scheduler Programming" page, yet it still casts this error. Any ideas?

Code:

[09:08:10 ERROR]: Nag author: 'cereal' of 'Vault' about the following: This plugin is not properly shutting down its async tasks when it is being reloaded.  This may cause conflicts with the newly loaded version of the plugin
[09:08:10 ERROR]: Nag author: 'iiSnipez' of 'CombatLog' about the following: This plugin is not properly shutting down its async tasks when it is being reloaded.  This may cause conflicts with the newly loaded version of the plugin
[09:08:10 ERROR]: Nag author: 'SydMontague' of 'ImageMaps' about the following: This plugin is not properly shutting down its async tasks when it is being reloaded.  This may cause conflicts with the newly loaded version of the plugin
[09:08:10 ERROR]: Nag author: 'Minecrell <" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://github.com/Minecrell>" rel="nofollow">https://github.com/Minecrell>' of 'ServerListPlus' about the following: This plugin is not properly shutting down its async tasks when it is being reloaded.  This may cause conflicts with the newly loaded version of the plugin
[09:08:10 ERROR]: Nag author: 'Minecrell <" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://github.com/Minecrell>" rel="nofollow">https://github.com/Minecrell>' of 'ServerListPlus' about the following: This plugin is not properly shutting down its async tasks when it is being reloaded.  This may cause conflicts with the newly loaded version of the plugin
[09:08:10 ERROR]: Nag author: 'cereal' of 'Vault' about the following: This plugin is not properly shutting down its async tasks when it is being reloaded.  This may cause conflicts with the newly loaded version of the plugin
[09:08:10 ERROR]: Nag author: 'dmulloy2' of 'ProtocolLib' about the following: This plugin is not properly shutting down its async tasks when it is being reloaded.  This may cause conflicts with the newly loaded version of the plugin
[09:08:10 ERROR]: Nag author: 'SydMontague' of 'ImageMaps' about the following: This plugin is not properly shutting down its async tasks when it is being reloaded.  This may cause conflicts with the newly loaded version of the plugin
[09:08:10 ERROR]: Nag author: 'iiSnipez' of 'CombatLog' about the following: This plugin is not properly shutting down its async tasks when it is being reloaded.  This may cause conflicts with the newly loaded version of the plugin
[09:08:10 ERROR]: Nag author: 'AnjoCaido' of 'GroupManager' about the following: This plugin is not properly shutting down its async tasks when it is being reloaded.  This may cause conflicts with the newly loaded version of the plugin
[09:08:10 ERROR]: Nag author: 'swifteh' of 'GAListener' about the following: This plugin is not properly shutting down its async tasks when it is being reloaded.  This may cause conflicts with the newly loaded version of the plugin
[09:08:10 ERROR]: Nag author: 'Minecrell <" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://github.com/Minecrell>" rel="nofollow">https://github.com/Minecrell>' of 'ServerListPlus' about the following: This plugin is not properly shutting down its async tasks when it is being reloaded.  This may cause conflicts with the newly loaded version of the plugin

Thanks,
~ Orcane

 

Oh, Actually I missed out a rather important piece of information, I only get these errors when I reload the server, and all the code works fine, even with the runnable, yes.

(And I fixed the "OnJoin" method xD)

 

"When you comment out the code that is responsible for your runnable and the names don't change: then ignore it" I don't think I quite understand what you mean by that.

"But: restart, don't reload." Everyone keeps telling me that, but convenienceee

 

Sorry, What list are we talking about?

 

Alright, every time I reload the server, the list of plugins that have the "Nag author:" is different though. This is bad then? And you said, "Make sure that your plugin won't start a runnable anymore." Why is that?

Thanks for your help btw, it is appreciated

 

Ahh, That's good to know, Thank you a lot for your help!