Why can't we use protected final in Loader so that we can inherit the attributes for recycled loader? about 2122-s2

[szeying02]

The attributes can be super() into RecycledLoader even if you use private final. Furthermore, I believe that we defined the getter methods to access these attributes in the sub-class RecycledLoader, so there really isn't a need to use protected final. This combined with the possibility that codecrunch would automatically reject all non- private final attributes (part of CS2030 scope I think), is why protected final wouldn't work. Hope this helps!

[Swagston20]

Thanks, I know what you said can be done. But why not make life easier and use protected final so that the sub class can access. I just want to know the rationale in encouraging us to not use protected final

[jingyulim1]

I think it is to strictly maintain the abstraction barrier. In case we have more subclasses in the future and we may not want the other subclasses to be able to access the information. Also, if we directly use the attribute from loader, if we were to change the representation in loader, then we may have to make neccessary changes everywhere else too.

[haoyangw]

For me I think it's cos the attributes in Loader are associated/shared with all Loaders, not just any specific subclass like RecycleLoader? So by restricting us to private final in the superclass Loader, this reminds us to distinguish between declaring e.g. Loader loader = new RecycleLoader() instead of RecycleLoader recycleLoader = new RecycleLoader() if we are trying to access shared attributes, and declaring RecycleLoader recycleLoader = new RecycleLoader() if we want to access the extended variables and methods (only) RecycleLoader provides(but Loader doesn't)?

This kind of sounds like Dependency Inversion Principle in a sense, cos you depend on the superclass Loader wherever possible instead of depending on RecycleLoader directly. This way your code that deals with shared attributes doesn't have to change if you only change the subclass(es) like RecycleLoader, you just update code that access extended attributes

[undeser]

It is to maintain the Abstraction Barrier.
Personally, it is a habit of mine to create getter functions, that way I can "legally" refer to the private attributes.