BlindnessTest.java

package io.notoh.BlindnessTest;

import org.bukkit.command.Command;
import org.bukkit.command.CommandExecutor;
import org.bukkit.command.CommandSender;
import org.bukkit.entity.Player;
import org.bukkit.plugin.java.JavaPlugin;
import org.bukkit.potion.PotionEffect;
import org.bukkit.potion.PotionEffectType;

/**
 * @author Notoh
 */
public class BlindnessTest extends JavaPlugin {

    public void onEnable(){
        getCommand("blindme").setExecutor((new CommandExecutor() {
            @Override
            public boolean onCommand(CommandSender sender, Command command, String label, String[] args) {
                if(sender instanceof Player) {
                    Player player = (Player) sender;
                    PotionEffect potionEffect = new PotionEffect(PotionEffectType.BLINDNESS,10,1);
                    player.addPotionEffect(potionEffect);
                    while(potionEffect.getDuration() != 0) {
                        //wait
                    }
                    player.addPotionEffect(new PotionEffect(PotionEffectType.BLINDNESS,10,1));
                    player.addPotionEffect(new PotionEffect(PotionEffectType.SPEED,10,1));
                    return true;
                } else {
                    return false;
                }
            }
        }));
    }
}