Java: Interface vs. Abstract Class

Interface

Features

• Multiple inheritance
• Does not provide any code
• static final constants
• A class implements an Interface
• Usually describe peripheral abilities of a class

Example

An Automobile class can implement an Automatic interface.

When To Use

Usually when something in the design will change frequently, such as a file format.

Abstract Class

Features

• Single inheritance
• complete, default, or stubs of code to be overwritten
• instance and static constants
• A class extends an Abstract Class
• Defines the core identity of it's descendants

Example

A SportsCar class can extend an Automobile abstract class.

When To Use

For planned inheritance hierarchies such as a framework or when subclasses need to provide specific behaviors.