Bukkit Holograms

public class Hologram {

   private static final double distance = 0.25;
   private List<String> lines = new ArrayList<String>();
   private List<Integer> ids = new ArrayList<Integer>();
   private boolean showing = false;
   private Location location;

   public Hologram(String... lines) {
      this.lines.addAll(Arrays.asList(lines));
   }

   public void change(String... lines) {
      destroy();
      this.lines = Arrays.asList(lines);
      show(this.location);
   }

   public void show(Location loc) {
      if (showing == true) {
         try {
            throw new Exception("Is already showing!");
         } catch (Exception e) {
            e.printStackTrace();
         }
      }
      Location first = loc.clone().add(0, (this.lines.size() / 2) * distance, 0);
      for (int i = 0; i < this.lines.size(); i++) {
         ids.addAll(showLine(first.clone(), this.lines.get(i)));
         first.subtract(0, distance, 0);
      }
      showing = true;
      this.location = loc;
   }

   public void show(Location loc, long ticks) {
      show(loc);
      new BukkitRunnable() {
         @Override
         public void run() {
            destroy();
         }
      }.runTaskLater(MMGames.getPlugin(), ticks);
   }

   public void destroy() {
      if (showing == false) {
         try {
            throw new Exception("Isn't showing!");
         } catch (Exception e) {
            e.printStackTrace();
         }
      }
      int[] ints = new int[this.ids.size()];
      for (int i = 0; i < ints.length; i++) {
         ints[i] = ids.get(i);
      }
      PacketPlayOutEntityDestroy packet = new PacketPlayOutEntityDestroy(ints);
      for (Player player : Bukkit.getOnlinePlayers()) {
         ((CraftPlayer) player).getHandle().playerConnection.sendPacket(packet);
      }
      showing = false;
      this.location = null;
   }

   private static List<Integer> showLine(Location loc, String text) {
      WorldServer world = ((CraftWorld) loc.getWorld()).getHandle();
      EntityWitherSkull skull = new EntityWitherSkull(world);
      skull.setLocation(loc.getX(), loc.getY() + 1 + 55, loc.getZ(), 0, 0);
      ((CraftWorld) loc.getWorld()).getHandle().addEntity(skull);

      EntityHorse cow = new EntityHorse(world);
      cow.setLocation(loc.getX(), loc.getY() + 55, loc.getZ(), 0, 0);
      cow.setAge(-1700000);
      cow.setCustomName(text);
      cow.setCustomNameVisible(true);
      PacketPlayOutSpawnEntityLiving packedt = new PacketPlayOutSpawnEntityLiving(cow);
      for (Player player : loc.getWorld().getPlayers()) {
         EntityPlayer nmsPlayer = ((CraftPlayer) player).getHandle();
         nmsPlayer.playerConnection.sendPacket(packedt);

         PacketPlayOutAttachEntity pa = new PacketPlayOutAttachEntity(0, cow, skull);
         nmsPlayer.playerConnection.sendPacket(pa);
      }
      return Arrays.asList(skull.getId(), cow.getId());
   }

}