@EventHandler
	public void onEntityDamage(EntityDamageByEntityEvent event) {
		if (event.getDamager().getType() != EntityType.PLAYER || event.getEntity().getType() != EntityType.PLAYER) {
			return;
		}
		Player player = (Player) event.getDamager();

		final String world_name = player.getWorld().getName();
		if (Main.worlds.contains(world_name)) {
			if ((player.getItemInHand() != null) && (player.getItemInHand().getEnchantments().containsKey(Enchantment.KNOCKBACK))) {
				player.sendMessage("§cKnockback jest wylaczony w endzie §5☹ §cNie umiesz sie inaczej klepac?");
				event.setCancelled(true);
			} else if ((player.getInventory().getItemInOffHand() != null)
					 && (player
							.getInventory().getItemInOffHand().getEnchantments().containsKey(Enchantment.KNOCKBACK))) {
				player.sendMessage("§cKnockback jest wylaczony w endzie §5☹ §cNie umiesz sie inaczej klepac?");
				event.setCancelled(true);
			}
		}
	}