Hilbert.java

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

/*************************************************************************
 *  Compilation:  javac Hilbert.java
 *  Execution:    java Hilbert N
 *  Dependencies: StdDraw.java
 *  
 *  Plot an order N Hilbert curve using two mutually recursive functions.
 *
 *  % java Hilbert 5
 *
 *
 *************************************************************************/

public class Hilbert {
    private Turtle turtle;

    public Hilbert(int N) {
        turtle = new Turtle(0.5, 0.5, 0.0);
        double max = Math.pow(2, N);
        turtle.setXscale(0, max);
        turtle.setYscale(0, max);
        hilbert(N);
    }


    // Hilbert curve
    private void hilbert(int n) {
        if (n == 0) return;
        turtle.turnLeft(90);
        treblih(n-1);
        turtle.goForward(1.0);
        turtle.turnLeft(-90);
        hilbert(n-1);
        turtle.goForward(1.0);
        hilbert(n-1);
        turtle.turnLeft(-90);
        turtle.goForward(1.0);
        treblih(n-1);
        turtle.turnLeft(90);
    }

    // evruc trebliH
    public void treblih(int n) {
        if (n == 0) return;
        turtle.turnLeft(-90);
        hilbert(n-1);
        turtle.goForward(1.0);
        turtle.turnLeft(90);
        treblih(n-1);
        turtle.goForward(1.0);
        treblih(n-1);
        turtle.turnLeft(90);
        turtle.goForward(1.0);
        hilbert(n-1);
        turtle.turnLeft(-90);
    }

    
    // plot a Hilber curve of order N
    public static void main(String[] args) {
        int N = Integer.parseInt(args[0]);
        new Hilbert(N);
   }
}