SierpinskiArrowhead

import java.awt.Graphics;

public class SierpinskiArrowhead extends FractalPainter {
    private static final double ANGLE = Math.PI / 3.0;

    @Override
    public void paint(Graphics g, int x, int y, int length, int order) {
        turtle.reset(x, y);
        int sign = 1;
        sa(g, length, order, sign);
    }

    public void sa(Graphics g, int length, int order, int sign) {
        if (order == -1) {
            turtle.move(g, length);
        } else {
            length /= 2;
            order -= 1;

            turtle.turn(sign * ANGLE);
            sa(g, length, order, -sign);
            turtle.turn(-sign * ANGLE);
            sa(g, length, order, sign);
            turtle.turn(-sign * ANGLE);
            sa(g, length, order, -sign);
            turtle.turn(sign * ANGLE);
        }
    }
}