Ryan Raina wrote:Why does it give implemention or say why to have it in first place??
Usually because it's a convenience for the developer.
If you look at the docs for AbstractSequentialList, you'll notice that it says in the very first sentence:
"This class provides a skeletal implementation of the List interface to minimize the effort required to implement this interface backed by a "sequential access" data store (such as a linked list)."
and I've certainly found the AbstractList class extremely useful.
As to why LinkedList overrides all the implementations, you'd have to ask the designer of the class. I hate to say, but "why" questions like this based on looking at source code will almost always get the same answer, because any guess on our part would be pure speculation.
I'd also suggest that looking at foundation class source code may not be the best use of your time, because the whole point about object-orientation is to
hide implementation - and whatever you do, NEVER write programs that
rely on source code that you've looked at.
If you want to get information on programming techniques, you'd be far better of getting a decent book on the subject.
Winston
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