Help me make this into a .jar file

Here is the code, could someone do this for me cause Its not letting me

Code:

import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import me.confuser.barapi.BarAPI;

import org.bukkit.Bukkit;
import org.bukkit.ChatColor;
import org.bukkit.entity.Player;
import org.bukkit.event.EventHandler;
import org.bukkit.event.Listener;
import org.bukkit.event.player.PlayerJoinEvent;
import org.bukkit.plugin.java.JavaPlugin;
public class Example extends JavaPlugin implements Listener {

    private Random r = new Random();

    private List<String> list = new ArrayList<>();

    public void onEnable() {
        list.add(colorize("&1 JOIN THE"));
        list.add(colorize("&2 JOIN THE"));

        showBarChanging();
    }

    private String colorize(String input) {
        return ChatColor.translateAlternateColorCodes('&', input);
    }

    public void showBarChanging() {
    Bukkit.getScheduler().scheduleSyncRepeatingTask(this, new Runnable() {
            public void run() {
                String message = (String) list.get(r.nextInt(list.size()));

                 for (Player p : Bukkit.getOnlinePlayers()) {
                     BarAPI.setMessage(p, message);
                 }
             }
         }, 0, 1 * 20);
     }
}

 

@timtower it says Error.

 

@amaranone Where's your onDisable() method?

 

@Gerov Its supposed to stay on at all times. Could you make it into a jar for me?

 

Overriding the onDisable method is not required.

 

@amaranone, that could not possibly be any more vague. What kind of error is it? Java syntax, invalid SDK, ect.

 

@amaranone If you're talking about the error you get when you export it, it's ok. It still makes it into a jar.

 

@Tecno_Wizard Wizard the error is Invalid SDK
@glasseater ots an Invalid SDK so idk

 

@amaranone download the JDK and build with it.