Tree java in a pgm

Tree.java

public class Tree

{

  public static void tree(int n, double x, double y, double a, double   branchRadius)

    {

        double bendAngle   = Math.toRadians(15);

        double branchAngle = Math.toRadians(37);

        double branchRatio = .65;

        double cx = x + Math.cos(a) * branchRadius;

        double cy = y + Math.sin(a) * branchRadius;

        StdDraw.setPenRadius(.001 * Math.pow(n, 1.2));

        StdDraw.line(x, y, cx, cy);

        if (n == 0) return;

        tree(n-1, cx, cy, a + bendAngle - branchAngle, branchRadius * branchRatio);

        tree(n-1, cx, cy, a + bendAngle + branchAngle, branchRadius * branchRatio);

        tree(n-1, cx, cy, a + bendAngle,              

        branchRadius * (1 - branchRatio));

  }

   public static void main(String[] args)

   {

        int N = Integer.parseInt(args[0]);

        StdDraw.show(0);

        tree(N, .5, 0, Math.PI/2, .3);

        StdDraw.show(0);

    }

}