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Abstract Classes vs Interfaces

Answer»

Abstract CLASS and Interface both are used for ABSTRACTION which is HIDING the background details and representing only the essential features. But there are major DIFFERENCES between abstract classes and interfaces. These are given as follows:

Parameter
Abstract Classes
 Interfaces
Instance Variables
Can have instance variables
Cannot have instance variables
Visibility
Can have any visibility:public, private or protected
Have either public visibility or no visibility
NATURE of methods
Can have both abstract as well as non-abstract methods
Only have abstract methods
Constructors
Can have constructors
Cannot have constructors
Association
Can be extended by using keywords ‘extends’
Can be implemented by using keyword ‘implements’
Nature of Association by Java class
A Java class can extend only one abstract class
A Java class can implement multiple interfaces
Provision of code
Can provide complete code
Just provide the signature/prototype


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