hilbertcurve | maps between 1-D space filling hilbert curve and N-D | Game Engine library

Here's my answer I just get.

Your fractal code bifurcation in HilbertCurve() looks good, so I'm guessing the problem has to do with your computation of step in the main() method.

Here's a different approach where I've used worldCoordinates() to change the coordinate system to match the problem (otherwise you need to know the size of the window -- something you left out of your step calculation.) I also coalesced the halves of HilbertCurve() into one by passing an angle value of 90 or -90 instead of branching off the parity of n. (Just for variety.)

Your turtle library is different from the one I found so you will need to adjust the code accordingly. You should state where you got your turtle library when asking a question like this.

Basically speaking, you want to decouple the data from the view. The way in which the data "might" be rendered should be irrelevant to the data.

This concept is commonly know as "Model-View-Controller".

To start with, you want to create a model of your "Hilbert Curve", which would be a bunch of points, each point representing the next point in the curve, for example...

First, I would suggest you start by reading through Performing Custom Painting and Painting in AWT and Swing to better understand how painting works in Swing.

The example Applet is actually a bad example of how to perform painting, as you should never maintain a reference to Graphics and it should be passed to the methods which need it when the component is painted.

You should also end up with a NullPointerException as sg is never initialised.

As a general rule, establish the UI first, then call setVisible last, it will solve a number of simple issues.

There's no reason HilbertCurve needs a reference to the JFrame, the frame can be instantiated in the main method instead.