Bresenham Circle

public abstract class Circle {

    public void create(int x0, int y0, int r) {
        int x = r, y = 0, e = 1-x;
        while(x >= y) {
            draw(x0 + x, y0 + y);
            draw(x0 + y, y0 + x);
            draw(x0 - x, y0 + y);
            draw(x0 - y, y0 + x);
            draw(x0 + x, y0 - y);
            draw(x0 + y, y0 - x);
            draw(x0 - x, y0 - y);
            draw(x0 - y, y0 - x);
            ++y;
            if (e < 0)
                e += (y << 2) + 1;
            else
                e += y - --x + 1 << 2;
        }
    }

    public abstract void draw(int x, int y);

}