code: public void add(double x, double y) {
          if (x < minX) minX = x;
          if (y < minY) minY = y;
          if (x > maxX) maxX = x;
          if (y > maxY) maxY = y;
      }
docs: Ensure the point x,y is included in the bounding box.
  
  @param x x-coordinate
  @param y y-coordinate