public void visitNeighbour(AStarNode origin, int x, int y, int z) {
    int costFromStart = origin.getCostFromStart() + goal.getNodeCost(origin, x, y, z);
    int costToGoal = goal.distanceToGoal(x, y, z);
    int totalCost = costFromStart + costToGoal;

    // Check if on open/closed list
    // If yes, check if new path is more efficient (lower f value)
    // and update path if so.
    AStarNode foundNode = openList.findOpenNode(x, y, z);
    boolean foundCheaperPath = false;
    if (foundNode != null) {
      if (totalCost < foundNode.getTotalCost()) {
        foundCheaperPath = true;
        openList.removeNodeFromOpenList(foundNode);
      }
    } else {
      foundNode = closedList.findClosedNode(x, y, z);
      if (foundNode != null) {
        if (totalCost < foundNode.getTotalCost()) {
          foundCheaperPath = true;
          closedList.removeNodeFromClosedList(foundNode);
        }
      } else {
        // Node not found in open and closed list, thus put a
        // new one on the open list.
        foundNode = map.nodeAt(x, y, z);
        foundCheaperPath = true;
      }
    }

    if (foundCheaperPath) {
      foundNode.initialize(origin, costFromStart, costToGoal, totalCost, x, y, z);
      openList.addNodeToOpenList(foundNode);
    }
  }
  /*
   * (non-Javadoc)
   *
   * @see machine.AStarMachine#findPath()
   */
  public List<AStarNode> findPath(
      int startX, int startY, int startZ, int endX, int endY, int endZ) {
    if (map == null)
      throw new IllegalStateException(
          "The searched map must be specified before path search can be done.");
    if (this.goal == null)
      throw new IllegalStateException(
          "The goal object must be specified before path search can be done.");

    AStarNode goalNode = map.nodeAt(endX, endY, endZ);
    int goalDistance = this.goal.getNodeCost(goalNode, startX, startY, startZ);
    goalNode.initialize(null, goalDistance, 0, goalDistance, endX, endY, endZ);
    this.goal.setGoalNode(goalNode);

    AStarNode startNode = map.nodeAt(startX, startY, startZ);
    startNode.initialize(null, 0, goalDistance, goalDistance, startX, startY, startZ);
    openList.addNodeToOpenList(startNode);
    return AStar.findPath(openList, closedList, map, this.goal, nodePool, this);
  }