What is similarities/difference between an Abstract class and Interface?

By: Karthik Printer Friendly Format    

Answer: Differences are as follows:

•	Interfaces provide a form of multiple inheritance. A class can extend only one other class. 
•	Interfaces are limited to public methods and constants with no implementation. Abstract classes can have a partial implementation, protected parts, static methods, etc. 
•	A Class may implement several interfaces. But in case of abstract class, a class may extend only one abstract class. 
•	Interfaces are slow as it requires extra indirection to to find corresponding method in in the actual class. Abstract classes are fast.  


•	Neither Abstract classes or Interface can be instantiated. 

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