CalculatingPI.java

/* *****************************************************************************
 *  Name:              Ada Lovelace
 *  Coursera User ID:  123456
 *  Last modified:     October 16, 1842
 **************************************************************************** */

public class CalculatingPI {
    public static void main(String[] args) {
        int a = Integer.parseInt(args[0]);
        long trials = Long.parseLong(args[1]);
        double radius = 0.5 * a;
        StdDraw.setCanvasSize(a, a);
        StdDraw.setScale(-radius - 50, radius + 50);
        StdDraw.circle(0, 0, radius);
        StdDraw.square(0, 0, 0.5 * a);
        int point_inside_circle = 0;
        for (int i = 0; i < trials; i++) {
            double randomX = -radius + Math.random() * (2 * radius);
            double y = Math.sqrt(radius * radius - randomX * randomX);
            double randomY = -radius + Math.random() * (2 * radius);
            StdDraw.setPenColor(StdDraw.BLUE);
            StdDraw.point(randomX, randomY);
            if (Math.abs(randomY) <= y)
                point_inside_circle++;
        }
        double pi = (double) (4 * point_inside_circle) / trials;
        String s = "pi = (4 * point inside circle/ points inside square)" + " = " + pi;
        StdDraw.text(0, 0, s);
        System.out.println(pi);
    }
}