Chaos.java

Below is the syntax highlighted version of Chaos.java from §1.5 Input and Output.

/******************************************************************************
 *  Compilation:  javac Chaos.java
 *  Execution:    java Chaos trials [radius]
 *  Dependencies: StdDraw.java
 *
 *  Play chaos game on triangle to produce Sierpinski gasket.
 *  Plot trials points of the specified radius.
 *
 *  % java Chaos 10000
 *
 ******************************************************************************/

public class Chaos {

    public static void main(String[] args) {
        int trials = Integer.parseInt(args[0]);
        if (args.length == 2) {
            double radius = Double.parseDouble(args[1]);
            StdDraw.setPenRadius(radius);
        }

        double[] cx = { 0.000, 1.000, 0.500 };
        double[] cy = { 0.000, 0.000, 0.866 };
        double x = 0.0, y = 0.0;
        for (int t = 0; t < trials; t++) {
            int r = (int) (Math.random() * 3);
            x = (x + cx[r]) / 2.0;
            y = (y + cy[r]) / 2.0;
            if      (r == 0) StdDraw.setPenColor(StdDraw.RED);
            else if (r == 1) StdDraw.setPenColor(StdDraw.GREEN);
            else if (r == 2) StdDraw.setPenColor(StdDraw.BLUE);
            StdDraw.point(x, y);
        }
    }
}