You reduced the "Square" class to a convenient implementation helper. Whatever type they choose to use, clients of your class hierarchy now only see one interf

You reduced the "Square" class to a convenient implementation helper. Whatever type they choose to use, clients of your class hierarchy now only see one interface: getWidth/getHeight. And they can't make assumptions based on the type they see, as both "Square" and "Rectangle" might have "getWidth()!=getHeight()". So they must handle the generic "rectangular" case. So, for the client, there's absolutely no visible difference between a "Square" or a "Rectangle". Which means there's no point in dealing with two classes anymore : all client code will then take "Square" objects, and deal with them as geometrical rectangles.