From so many replies, the difference betn Interface and abstract class might be clear. One more advantage i see in
using the interface is the great flexibility. If u are providing an interface for any product and leave the implementation on different vendors then it will be feasible for everybody. For e.g. ODBC drivers etc.

To put it simply, if u have designed some database then u will definitely be providing the apis which will access it.
But it's won't be feasible for u to provide the api's which
will be used by any language or tool which will be coming in future and using ur database product. But if u provide an interface then any other product using ur database product will give it's own api definition implementing the interfact provided by u. This will keep the user who is coding from the intricasies of the deployment.

But in true sense it's really the business need which decides the use of abstract class or interface.


cheers,

sachin.

From so many replies, the difference betn Interface and abstract class might be clear. One more advantage i see in
using the interface is the great flexibility. If u are providing an interface for any product and leave the implementation on different vendors then it will be feasible for everybody. For e.g. ODBC drivers etc.

To put it simply, if u have designed some database then u will definitely be providing the apis which will access it.
But it's won't be feasible for u to provide the api's which
will be used by any language or tool which will be coming in future and using ur database product. But if u provide an interface then any other product using ur database product will give it's own api definition implementing the interfact provided by u. This will keep the user who is coding from the intricasies of the deployment.

But in true sense it's really the business need which decides the use of abstract class or interface.


cheers,

sachin.

For instance,
if you are developing a tool or a component that you would want someone to use, then I would choose both the interface and the abstract class approach.
typically the strategy followed by java swing classes.
It has an interface, an abstract class implementing that interface and a default class extending the abstract class.
The users of this component has got 3 options to choose from based on his requirement.

interface approach gives you flexibility, since you are the one who will be providing the implementation. but at the same you need to be worried about the implementation details.
abstract class gives you simplicity, since you are going to inherit the implementation.

This question is very much debatable, and can be answered convincingly only if there are specific requirements.

Yes, I use both together, frequently.