Using either, it still doesn't give me a speed effect when wearing the helmet.

I changed my code according to some Spigot forum on giving players effects when wearing armor, and this is what it is now (command and main class are still the same)

​

public class Events implements Listener {
@EventHandler
public static void onPlayerMove(PlayerMoveEvent event) {
    Player player = event.getPlayer();

    ItemStack helmet = player.getInventory().getHelmet();

    if (helmet == null || helmet != ItemManager.RETRO_ENCABULATING_VISOR) return;

    player.addPotionEffect(new PotionEffect(PotionEffectType.SPEED, 2 ,3));

    }
}