What is the purpose of garbage collection in Java, and when is it used? What is the purpose of garbage collection in Java, and when is it used? Abstract classes and interfaces are often compared and can sometimes do the same thing.
Abstract classes are base classes where the derived class must implement the methods of that abstract class. However, children of those 'derived' classes do not have to implement the methods of the original base class (abstract class). Furthermore, abstract classes form a 'is-a' relationship, meaning the derived classes "are" of type ...(abstract)...Ex: a Shapes abstract base class and a square derived class. A square is a shape.
Interfaces are different - they are simply guidelines and rules that must be followed by any and all classes that implement them. If you create a class that implements an interface, it must include all the methods in that interface. Then if you go to derive that class, you could overwrite the methods or leave them (as they will have already been implemented in the base class).
Interfaces are not a 'is-a' relationship. For example, you could have a Size interface. A square is not a size, but your square class must implement various size methods (volume, surface area).

Answered by Raksha , an ibibo Master, at 8:31 AM on June 26, 2008

well jiks, The difference betweeninterface and abstract class are given below-
1. An abstract class can have instance methods that implement a default behavior.
An Interface can only declare constants and instance methods, but cannot implement default behavior and all methods are implicitly abstract.

2.An interface has all public members and no implementation. An abstract class is a class which may have the usual flavors of class members (private, protected, etc.), but has some abstract methods.

Answered by Romi , an ibibo Master, at 6:38 PM on June 17, 2008

Hi,

Definition: An interface is a named collection of method definitions (without implementations). An interface can also declare constants.


-An interface cannot implement any methods, whereas an abstract class can.

-A class can implement many interfaces but can have only one superclass.

-An interface is not part of the class hierarchy. Unrelated classes can implement the same interface.

Answered by Ajay Pal , an ibibo Master, at 4:14 PM on June 02, 2008

What is the purpose of garbage collection in Java, and when is it used? What is the purpose of garbage collection in Java, and when is it used? Abstract classes and interfaces are often compared and can sometimes do the same thing.
Abstract classes are base classes where the derived class must implement the methods of that abstract class. However, children of those 'derived' classes do not have to implement the methods of the original base class (abstract class). Furthermore, abstract classes form a 'is-a' relationship, meaning the derived classes "are" of type ...(abstract)...Ex: a Shapes abstract base class and a square derived class. A square is a shape.
Interfaces are different - they are simply guidelines and rules that must be followed by any and all classes that implement them. If you create a class that implements an interface, it must include all the methods in that interface. Then if you go to derive that class, you could overwrite the methods or leave them (as they will have already been implemented in the base class).
Interfaces are not a 'is-a' relationship. For example, you could have a Size interface. A square is not a size, but your square class must implement various size methods (volume, surface area).
In the long run, you will probably use interfaces more often if you are looking at polymorphism and attempting to force classes to include certain methods.

Answered by ayisha , an ibibo Master, at 6:19 PM on June 01, 2008

An abstract class can have instance methods that implement a default behavior.
An Interface can only declare constants and instance methods, but cannot implement default behavior and all methods are implicitly abstract. An interface has all public members and no implementation.
An abstract class is a class which may have the usual flavors of class members (private, protected, etc.), but has some abstract methods.

For example, if you have an application framework, an abstract class may provide default services such as event and message handling. Those services allow your application to plug in to your application framework. However, there is some application-specific functionality that only your application can perform. Such functionality might include startup and shutdown tasks, which are often application-dependent. So instead of trying to define that behavior itself, the abstract base class can declare abstract shutdown and startup methods. The base class knows that it needs those methods, but an abstract class lets your class admit that it doesn't know how to perform those actions; it only knows that it must initiate the actions.

Answered by Madhurima , an ibibo Master, at 1:08 PM on May 31, 2008

Definition: An interface is a named collection of method definitions (without implementations). An interface can also declare constants.

-An interface cannot implement any methods, whereas an abstract class can.
-A class can implement many interfaces but can have only one superclass.
-An interface is not part of the class hierarchy. Unrelated classes can implement the same interface.

Answered by manu pal , an ibibo Citizen, at 5:45 AM on May 29, 2008

well Marven, An abstract class can have instance methods that implement a default behavior.
An Interface can only declare constants and instance methods, but cannot implement default behavior and all methods are implicitly abstract. An interface has all public members and no implementation.
An abstract class is a class which may have the usual flavors of class members (private, protected, etc.), but has some abstract methods.

For example, if you have an application framework, an abstract class may provide default services such as event and message handling. Those services allow your application to plug in to your application framework. However, there is some application-specific functionality that only your application can perform. Such functionality might include startup and shutdown tasks, which are often application-dependent. So instead of trying to define that behavior itself, the abstract base class can declare abstract shutdown and startup methods. The base class knows that it needs those methods, but an abstract class lets your class admit that it doesn't know how to perform those actions; it only knows that it must initiate the actions.

Answered by Uttam , an ibibo Master, at 8:44 PM on May 28, 2008

The difference betweeninterface and abstract class are given below-
1. An abstract class can have instance methods that implement a default behavior.
An Interface can only declare constants and instance methods, but cannot implement default behavior and all methods are implicitly abstract.

2.An interface has all public members and no implementation. An abstract class is a class which may have the usual flavors of class members (private, protected, etc.), but has some abstract methods.

Answered by Nagendra , an ibibo Master, at 5:53 PM on May 28, 2008

abstract class is a class that serves only as a base class from which classes are derived. no objects of an abstract base class are created. a base class that contains pure virtual functions is an abstract base class.

interface is the visible method of an object

Answered by Nishu's , an ibibo Master, at 2:35 PM on May 28, 2008

Choosing interfaces and abstract classes is not an either/or proposition. If you need to change your design, make it an interface. However, you may have abstract classes that provide some default behavior. Abstract classes are excellent candidates inside of application frameworks.

Abstract classes let you define some behaviors; they force your subclasses to provide others. For example, if you have an application framework, an abstract class may provide default services such as event and message handling. Those services allow your application to plug in to your application framework. However, there is some application-specific functionality that only your application can perform. Such functionality might include startup and shutdown tasks, which are often application-dependent. So instead of trying to define that behavior itself, the abstract base class can declare abstract shutdown and startup methods. The base class knows that it needs those methods, but an abstract class lets your class admit that it doesn't know how to perform those actions; it only knows that it must initiate the actions. When it is time to start up, the abstract class can call the startup method. When the base class calls this method, Java calls the method defined by the child class.

Answered by Om Prakash , an ibibo Master, at 2:32 PM on May 28, 2008