Answer / sumit gupta

the basic logical difference is you create abstract class when there is a relation between two classes that will inherit the abstract class and you create interface for the classes which are not related to each other but do have some common functionality.

below link describes it quite nicely.

http://devworkexperience.com/2011/09/interfaces-vs-abstract-classes/

Answer / killer

An abstract class is a special kind of class It allow other
classes to inherit but cannot be instantiated. It Inherit
only one abstract class.

An interface is similar to Abstract class, it cannot use
override keyword in inheritance class. It inherits several
interfaces.

Answer / arunachalam.m

To inherit the more than one interface class.... But in
abstract onle one abstract class can be inherit them....

Answer / ravi anand pathak

1)-Abstract class required two key word for declaring
abstract class.
Interface required interface keyword for declaring the
interface.
2)-Within abstract class we can declare concrite and
abstract both type of method.
Interface support only abstract method.
3)-Variable declared within abstract class are normal.
All variables are emplicitly final,public static within
interface.
4)-We required abstract keyword to declared abstract
keyword.
All methods areemplicitlypublic and abstract.
5)-We use extends kyeword to inheriate any abstract class.
We use implements kyeword to use interfaces.
6)-Only one abstract class can extends at a time(single
inheritence).
We can use multipleinterface in a class at asame time(just
like multiple overriding).

Answer / penchalaramaiah

An Abstract class have an implementation but an interface should not any implementation and it contains only definition
and interface contains by default abstract methods but an abstract class contains subclassess

Answer / braham dutt

Abstract classes can have implementations for some of its
members (Methods), but the inteface class can't have
implementation for any of its members.

Abstract classes are faster than interfaces.
Interface comes in Inheritance chain while Abstract not.

Answer / ramana

abstract class is about to have defined and undefined methods.but in case of interfaces ,only method declarations are avaliable.abstract class can't support multiple inheritance but interfaces can support.

Answer / abi

In Abstract class we can do implementation for its methods
but in interface we can not do implemantations for any of
ti's methods

Answer / malar

In Abstract class:We cant create the instance for abstract
class..
In Interface:It allow to create the instance through
implementing classes...

Answer / ramani krunal

1. interface contains methods that must be abstract;
abstract class may contain concrete methods.
2. interface contains variables that must be static and
final; abstract class may contain non-final and final variables.
3. members in an interface are public by default,
abstract class may contain non-public members.
4. interface is used to "implements"; whereas abstract
class is used to "extends".
5. interface can be used to achieve multiple inheritance;
abstract class can be used as a single inheritance.
6. interface can "extends" another interface, abstract
class can "extends" another class and "implements" multiple
interfaces.
7. interface is absolutely abstract; abstract class can
be invoked if a main() exists.
8. interface is more flexible than abstract class because
one class can only "extends" one super class, but
"implements" multiple interfaces.
9. If given a choice, use interface instead of abstract
class.

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