Need help using StdDraw to draw a 2D array

Question

So I already have a method which reads a file which I have converted into a 2d array(therefore the dimensions of the array could be different each time depending on which file I use). Now I am trying to draw a rectangle using this and it wont work. My code is:

public static void drawBoard(String [][] board)  {

    for (int i = 0; (i < board.length); i++) { //line 88
        for (int j = 0; (j < board[0].length); j++) {
            int r = board.length;
            int c = board[0].length;
            double R = new Double(r);
            double C = new Double(c);

        StdDraw.setXscale(0,C);
        StdDraw.setYscale(0,R);
        StdDraw.setCanvasSize(500,500);
        StdDraw.setPenRadius(0.05);
        StdDraw.setPenColor(StdDraw.BLUE);
        StdDraw.rectangle((C/2), (R/2), (C/2), (R/2));
        StdDraw.close();


    }
}
}

What can I do to fix this? How can I get it to draw a rectangle? it says the error is in line 88 and that its a "java.lang.NullPointerException" error.

Answer 1

StdDraw.rectangle expects input parameters of type double. You pass it input parameters of type int. This is ok but you might not want to do this. When calculating C/2 and R/2 you do integer division and thus you might accidentially round down. To fix this, you could initialize C and R as double.