Ngon.java

Below is the syntax highlighted version of Ngon.java from §3.2 Creating Data Types.

/******************************************************************************
 *  Compilation:  javac Ngon.java
 *  Execution:    java Ngon n
 *  Dependencies: Turtle.java
 *
 *  Plots a regular n-gon.
 *
 *  The side length s of a regular n-gon inscribed in a circle
 *  of diameter 1 is sin(pi/n).
 *
 ******************************************************************************/

public class Ngon {

    public static void main(String[] args) {
        int n = Integer.parseInt(args[0]);
        double angle = 360.0 / n;
        double step  = Math.sin(Math.toRadians(angle/2.0));   // sin(pi/n)
        Turtle turtle = new Turtle(0.5, 0.0, angle/2.0);
        for (int i = 0; i < n; i++) {
            turtle.goForward(step);
            turtle.turnLeft(angle);
        }

    }
}