Programming Tutorials

What is the difference between interface and abstract class?

By: Karthik  

• interface contains methods that must be abstract; abstract class may contain concrete methods.
• interface contains variables that must be static and final; abstract class may contain non-final and final variables.
• members in an interface are public by default, abstract class may contain non-public members.
• interface is used to "implements"; whereas abstract class is used to "extends".
• interface can be used to achieve multiple inheritance; abstract class can be used as a single inheritance.
• interface can "extends" another interface, abstract class can "extends" another class and "implements" multiple interfaces.
• interface is absolutely abstract; abstract class can be invoked if a main() exists.
• interface is more flexible than abstract class because one class can only "extends" one super class, but "implements" multiple interfaces.
• If given a choice, use interface instead of abstract class.

Archived Comments