code: public final int addPoint(Point2D<?, ?> point, int indexGroup) {
  		return addPoint(point.getX(), point.getY(), indexGroup);
  	}
docs: Add the specified point at the end of the specified group.
  
  @param point the new point.
  @param indexGroup the index of the group.
  @return the index of the point in the element.
  @throws IndexOutOfBoundsException in case of error.