15 puzzle using 2d arrays

I made a basic (not very efficient) algorithm to solve a 15-puzzle using bfs.
Each node is a puzzle-state.

I assume I'm doing something wrong, because the puzzles.size() runs over 30000+
I'd really appreciate it if someone could take a look.

It should basically go:

Code:

---

new queue, add rootNode
while (queue != empty){
    Node n = firstFromQueue
    if ( n matches goalState)
        succes
    else
        add n.successors to queue

---

but also keep track of the nodes visited, because you don't need to visit them again.

Add some debugging statements to show execution flow and how variable values change.

If you see how the code is executing, you should be able to see your problem.