code: public double getHeuristicCost(int stx, int sty, int dtx, int dty)
      {
          return heuristic.getCost(stx, sty, dtx, dty);
      }
docs: Get the heuristic cost for the given location. This determines in which order the locations are processed.
  
  @param stx The x coordinate of the tile whose cost is being determined
  @param sty The y coordinate of the tile whose cost is being determined
  @param dtx The x coordinate of the target location
  @param dty The y coordinate of the target location
  @return The heuristic cost assigned to the tile