In this Java 101 tutorial, I’ve explained how interfaces differ from classes, and showed you how to declare, implement, and extend interfaces in your Java programs.

Abstract classes and interfaces in Java serve fundamentally different purposes. Learn the differences between these Java language elements and how to use them in your programs.

Intro to Java Interfaces An interface is a reference type in Java. Interfaces are a completely abstract type that is used to specify a behavior that classes must implement.