public interface Draw {
  void drawLine(double x1, double y1, double x2, double y2);
}


public class DrawUtil {
  public static void drawBox(Draw draw, double x1, double y1, double width, double height) {
    draw.drawLine(x1, y1, x1 + width, y1);
    draw.drawLine(x1 + width, y1, x1 + width, y1 + height);
    draw.drawLine(x1 + width, y1 + height, x1, y1 + height);
    draw.drawLine(x1, y1 + height, x1, y1);
  }
}


public class SwingDraw implements Draw {
  // some code here
}

public class DXFDraw implements Draw {
  // some code here
}

public class MyThing {
  // drawMyThing can draw to the screen and be exported to DXF
  public void drawMyThing(Draw draw) {
    // some code here
  }
}