Interface Vs Abstract Class

[javarishi]

Can AnyOne Say, When Exactly, We Need To Go For An Abstract Class, And An

Interface? On Basis Of What We Need To Make A Decision?

[Eranga]

In my programming practice, if I want to change something on my design frequently, I go for an interface.

Abstract class used for some common behaviors.

[javarishi]

Thanks Eranga. Abstract Class Is Clear. In Case Of Interface, you mean to say if the method signature changes frequently, then we need to put it inside an interface? Can you please, brief me please?

[Eranga]

Yep, you are right. Say I have an interface like this,

Code:

interface Test{
   boolean isLess(Object a);
   boolean isSmall(Object a);
   boolean isEqual(Object a);
}

In all case I'm looking different implementation, with the same arguments actually. There are large number of such cases can be found in Java.

[ferranb]

Use abstract classes when you want to "force" to derived classes to implement some code.

Use interfaces when you want to define a behavior that can define any class that implement it on different hierarchies. When a class implements an interface is saying "I'm able to do that especific thing". When you subclass a class you are saying "I'm like my parent and more".

Ferran

Ferran

[sukatoa]

Abstract classes vs Interfaces