Additional lessons for the level

Why Java needs interfaces

In this lesson, we'll talk about an important concept in Java: interfaces. You're probably familiar with the word. For example, interfaces are part of most computer programs and games. In a broad sense, an interface is a kind of "control panel" that connects two interacting parties. See the lesson to learn what exactly this word means in Java.

Useful materials

As the author of this short series of articles writes, these materials will benefit those who have figured out how to create interfaces, understand how interface inheritance works, and have implemented several examples, but still do not understand the why. The material below addresses the "application" of interfaces:

• Why do we need interfaces?
• Why do I need interface inheritance?
• Java Polymorphism

The difference between abstract classes and interfaces

In this lesson, you'll learn how abstract classes differ from interfaces, and you'll see examples of common abstract classes.

The difference between an abstract class and an interface is important. You will be asked about the difference between these concepts in 90% of your future job interviews. So be sure you understand what you read.