Why abstract class is faster than interface

Do you know what a "virtual table" or "vtbl" is? Basically, a simple vtbl could be used for directly inherited methods, and so the JVM just had to look at two pointers to find the code for a method inherited from an abstract class -- that's relatively fast. But since any class can implement any number of interfaces, finding the code that implements an interface method would involve following a pointer to a table of interfaces implemented by a class, then searching through the table to find a vtbl for the implementation of that interface, and then finding the method pointer in the table.

That's obviously a lot more work, so calling an interface method used to be measurably slower. It can have multiple concrete methods. Abstract classes allow you to create blueprints for concrete classes. But the inheriting class should implement the abstract method. An abstract class permits you to make functionality that subclasses can implement or override whereas an interface only permits you to state functionality but not to implement it.

A class can extend only one abstract class while a class can implement multiple interfaces. Skip to content. Report a Bug. Can you include that link? I rather doubt that this conclusion is correct. Methods are identified using a table look up. Based on information that is fixed upon the class was loaded. There should be no conceptual difference between looking up methods via a table Don't believe all you read on the Internet.

GhostCat done : — Adelin. Add a comment. Active Oldest Votes. Improve this answer. Holger Holger k 33 33 gold badges silver badges bronze badges. Sign up or log in Sign up using Google. Sign up using Facebook. It is also referred to as static polymorphism Compile-time and dynamic polymorphism Runtime.

Inheritance is also used to inherit the base class members by a derived class. In C , an Abstract class vs interface C has been used for data abstraction. An interface is better than an abstract class when multiple classes need to implement the interface.

The member of the interface cannot be static. The only complete member of an abstract class can be static. C does not support multiple inheritances; interfaces are mainly used to implement the multiple inheritances. As a class can implement more than one interface and only inherit from one abstract class. An interface is mainly used only when we do not require the implementation of methods or functionalities.

An abstract class is used when we do require at least a default implementation. These both C Interface vs Abstract Class are great object-oriented programming concepts that are used highly in developing applications as per the requirement. It is purely selected by the technical leads with which they are more comfortable and the business requirement. Both are easy to use and simple to learn in any programming language.