A_star.java

    /// Gets the value of a tile.
    /**
     * Given an X and Y coordinate, returns the value of the tile at that position.
     * This function also marks that location as visited.  Part of your grade on this
     * assignment will be determined by how many tiles your solution visits.
     * 
     * @param x The X coordinate.
     * @param y The Y coordinate.
     * @return The value of the tile at that location.
     */
    public double getTile(final int x, final int y){
        if(!validTile(x, y)){
            throw new IndexOutOfBoundsException("Tried to access (" + x + ", " + y + ") " +
                                            "in a board of dimension " + Width + " x " + Height);
        }
        down();
        if(Uncovered[x][y] == 0){
            uncoveredCounter++;
            Uncovered[x][y] = uncoveredCounter;
        }
        up();
        return Board[x][y] & 0xFF;
    }

    public double getCost(final Point p1, final Point p2){
         // Only use of the the following dependent on question
         //return (double) (getTile(p1)) /  ( (double) getTile(p2)+1.0);
	     return Math.pow(2.0, (getTile(p2) - getTile(p1)));
    }

    /// Aquires the semaphore.
    private void down(){
        try{
            sem.acquire();
        }
        catch(InterruptedException ex){
            throw new RuntimeException("down function was interupted");
        }
    }

    /// Release the semaphore.
    private void up(){
        sem.release();
    }

// Board is a property defined like so: Board = terraGen.getTerrain();