Interfaces in Java

Today's notes - Interfaces

Terminology

interface

An interface specifies behavior for a class. - Gaddis definition

It is also the keyword that defines the interface

implements

the java keyword that indicates that a class is implementing a specified interface

Notes

• An interface provides a contract for a class's behaviors.
• interfaces provide method headers. May also provide constants. May not provide attributes (because these are not inherited).
• a class implementing an interface must implement each of the interface's methods...this is the contract.
• interfaces provide a "multiple inheritance" mechanism. It is not inheritance, but classes that implement the same interface can be treated as if they share the "is-a" relationship.
• interfaces may be extended. The method headers (contractual requirements) are inherited. Implementing classes must implement all methods in the child and all ancestors.
• interface methods are always public.

Syntax

declaration
 visibility interface name

using

visibility class name implements interfaceName

Examples