code: public void add (Area area) {
          if (area == null || area.isEmpty()) {
              return;
          } else if (isEmpty()) {
              copy(area, this);
              return;
          }
  
          if (isPolygonal() && area.isPolygonal()) {
              addPolygon(area);
          } else {
              addCurvePolygon(area);
          }
  
          if (areaBoundsSquare() < GeometryUtil.EPSILON) {
              reset();
          }
      }
docs: Adds the supplied area to this area.