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Message:

Re:

Posted by A.P on October 18, 2001 at 11:53 PM

Abstract classes have important distinction from interfaces.

interfaces cannot have method body. If base abstract class defines a method, a child does not have to redefine it unless it wants to.

> 1 ans) If you examine carefully abstract classes provide
> the defintion or skelton part for members so that any one can
> implement and custonmize the methods as per the requirements.

> cheers
> venu

> > I wish to ask you certain doubts . While reading the subject , I got the feeling that most of the books are written with the 'how' and not 'why' approach . And certain design aspects are left unanswered .
> > Like :
> > 1) why was there a need for 'abstract classes' when ( seemingly) all the functionality could be achieved by the use of interface / concrete classes ?
> > 2) why didn't Sun provide for multiple inheritance for classes and did it for interfaces - as far as I could reckon , there is virtually no difference between the two ( an interface is as good as an abstract class ) ? ( I am not particularly convinced with the argument that it makes the compilers complex - after all it does exit already in C++ compiler .)
> > 3) how do togging interfaces viz. 'cloneable', ' serializable' etc. work ; which do not have any methods declared ( or defined ) inside them. Also, are these not the examples of multiple inheritance in some way ?

> > There must be more design aspects which I have not been able to come up to. I request you to please tell me where I can the answer to these questions as well as a more in depth dealing about why Java is the way it is . Please suggest me the readable books on the topic .

• Java Design Matt Gerrans October 19, 2001 at 2:05 PM (0)