difference between abstact class and interface

Question

Accepted Answer

Abstract class is a class with implementation while interface is a contract without implementation.

Abstract class can have constructors while interface cannot
A class can implement multiple interfaces but can only inherit from one abstract class
Abstract class can have non-abstract methods while interface can only have abstract methods
Example of abstract class: Animal with method eat() implemented
Example of interface: Runnable with method run() defined

Accepted Answer

Abstract class	Interface
1) Abstract class can have abstract and non-abstract methods.	Interface can have only abstract static methods also.
2) Abstract class doesn't support multiple inheritance.	Interface supports multiple inheritance.
3) Abstract class can have final, non-final, static and non-static variables.	Interface has only static and final variables.
4) Abstract class can provide the implementation of interface.	Interface can't provide the implementation of abstract class.
5) The abstract keyword is used to declare abstract class.	The interface keyword is used to declare interface.
6) An abstract class can extend another Java class and implement multiple Java interfaces.	An interface can extend another Java interface only.
7) An abstract class can be extended using keyword "extends".	An interface can be implemented using keyword "implements".
8) A Java abstract class can have class members like private, protected, etc.	Members of a Java interface are public by default.
9)Example:public abstract class Shape{public abstract void draw();}	Example:public interface Drawable{void draw();}

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