Can only iterate over an array.... Miss understanding

I found some scripts but i always have problem applying them to my build of server,
I never had any other problems with other custom scripts, just cant get anitdual box work.
Most common to use is /* This program is free software; you can redistribute it and/or modify * it u - Pastebin.com
but when i just paste

Code:

---

public static void disc(final L2PcInstance player)
  {
      player.sendPacket(new CreatureSay(1, Say2.HERO_VOICE, "SYSTEM", "You cannot play with dualbox."));
      ThreadPoolManager.getInstance().scheduleGeneral(new Runnable()
      {
        public void run()
        {
            player.closeNetConnection();
        }
      }, 20000);
  }
  public static boolean check(L2PcInstance player)
  {
      boolean loggedz0r = false;
      for (L2PcInstance playerz0r : L2World.getInstance().getAllPlayers())

---

L2World.getInstance().getAllPlayers()) - eclipse gives me error on this line (It may sound stupid for some of you java proffesionals, but i actually have no idea what he want from me)
it say's "Can only iterate over an array or an instance of java.lang.Iterable"
I found some explanations in google, but it's not written in human language I actually couldn't understand what he wants from me.
Any one can suggest fix (Well better be a little explanation)

Post the method signature for getAllPlayers(). What is its return type?

db