Courses /

Java OOP

1. How to Work With IDE?

Installing IntelliJ IDEA (MacOS)

Installing IntelliJ IDEA (Windows)

Code Editor Main Features

Debugger

Packages

How to do Tasks?

2. OOP

Finally, we can start learning Object-Oriented Programming (OOP) in Java. It will be challenging, but I'm confident that you'll succeed! In this section, we'll cover all the principles of OOP, explain why OOP is important. You'll learn how to inherit classes, overload and override methods, encapsulate data from other classes, and work with abstraction. Moreover, you'll reinforce all these theoretical concepts with practical exercises, working on assignments in your IDE. You'll gain a wealth of knowledge, both practical and theoretical, so let's get started!

What is OOP?

OOP Principles: Inheritance

Challenge: Inheritance

OOP Principles: Polymorphism

Challenge: Polymorphism

OOP Principles: Encapsulation

OOP Principles: Abstraction

Challenge: Abstraction

3. Interface

In the previous section, we concluded that all Object-Oriented Programming is mainly built on abstraction. However, an abstract class has one significant limitation – you can inherit from only one abstract class. But what if we need more? Interfaces come to the rescue. In this section, you will learn what an interface is, why it's necessary, how to use it correctly, and you will continue practicing Object-Oriented Programming. Let's turn you into a professional!

What is Interface?

Challenge: Interface

Abstract Class vs Interface

Default Methods

Static Methods

Summary

Challenge: Abstraction

Task

An abstract class called Shape has been created for you. It contains two abstract methods: calculateArea() and calculatePerimeter(). Your task is to implement two classes: Rectangle and Circle. You need to inherit these classes from the abstract class Shape and override its methods. Here's a brief guide:

For the Circle class, you will need fields such as radius, and for the Rectangle class, you will need fields like width and height. These fields and their constructors are already provided for you. Use these fields when overriding the methods.
If you don't have strong geometry knowledge, here's a quick reference with formulas you need to use:
- Circle Area: Pi * radius * radius;
- Circle Perimeter: 2 * PI * radius;
- Rectangle Area: width * height;
- Rectangle Perimeter: 2 * (width + height).

To use the value of π (PI), make use of the Math library. You can use Math.PI to access the value of π.

Link to the task: GitHub

Use the @Override annotation to override both methods from the abstract class Shape: calculateArea() and calculatePerimeter().

For the Circle, utilize the formulas I mentioned above. To access the value of π, use Math.PI.

Use the syntax return "formula to calculate";.

Click the Run Tests button to check the correctness of your solution.

Everything was clear?

Section 2. Chapter 8

Challenge: Abstraction

Task

For the Circle class, you will need fields such as radius, and for the Rectangle class, you will need fields like width and height. These fields and their constructors are already provided for you. Use these fields when overriding the methods.
If you don't have strong geometry knowledge, here's a quick reference with formulas you need to use:
- Circle Area: Pi * radius * radius;
- Circle Perimeter: 2 * PI * radius;
- Rectangle Area: width * height;
- Rectangle Perimeter: 2 * (width + height).

To use the value of π (PI), make use of the Math library. You can use Math.PI to access the value of π.

Link to the task: GitHub

Use the @Override annotation to override both methods from the abstract class Shape: calculateArea() and calculatePerimeter().

For the Circle, utilize the formulas I mentioned above. To access the value of π, use Math.PI.

Use the syntax return "formula to calculate";.

Click the Run Tests button to check the correctness of your solution.

Everything was clear?

Section 2. Chapter 8