Horrible. You should learn about the definition of static cus its clear that you improperly use it. Regardless, it's not even a proper teleportation system, probably top basic stuff, I wouldn't recommend anyone using it but up to you. If you're looking to improve, yet again, you should maybe take some java courses online to avoid those mistakes.
Improper fix. Should map the data sent from the server to client and then verify when coming back from client to server. In your scenario, you could still somehow cheat (yet wont be really efficient) by creating rune items with bronze items; All you are doing is check if the item id given in the packet exists in the array, which is technically incorrect