Lessons

Congratulations on moving to the next stage of your studies at Java University. Ahead is a lot of new useful knowledge that will help you become a software development professional...

You've already heard about classes and objects. Now it's time to take a look at them from a different angle. Abstraction, encapsulation, inheritance, and polymorphism — perhaps these words currently don't mean anything to you (or perhaps their meaning is unrelated to programming). But before long you'll learn that OOP rests on these four pillars.

"OOP is cumbersome and clumsy! Is there no way around it?" is a common question often asked by CodeGym students at this stage. In this lesson, you'll hear a story about a company that ships goods to outer space. "And what does that have to do with OOP?" you ask. The fact that this approach helps the company cope with some challenges. It will help you, too.

The product's internal structure must be maintained in a way that will allow major (and minor) changes to be made with minimum reworking. Object-oriented programming lets companies work on huge projects without floundering when the code needs to be revised.

Valid internal state, argument checking, fewer bugs when changing code inside classes, the ability to define how objects interact with other objects... What are we talking about? These are the main advantages of encapsulation, one of the four pillars of OOP. Rishi Gatesman will tell you all about it.

Let's dedicate today's lesson to encapsulation and begin right away with examples :) Here you have an ordinary soda machine. I have one question for you: how does it work? Try to provide a detailed answer: where does the cup come from, how is the internal temperature maintained...

Upon completing this lesson, knowing what polymorphism is, you'll be able to settle parent-child problems, because you'll know what needs to be done if a child wants to use one of his forefathers' methods. In other words, you won't be confused by a whale with cow ancestry that can swim but lacks horns and a bell. You'll even be able to code one up.

A deep understanding of OOP and its key principles will help you better understand the structure of the Java language and write good code. This selection of resources includes several articles that will teach you OOP basics as well as some useful nuances...

You often need to define something unspecific and basic. For example, a "car". It will have an engine and vehicle body. This isn't a car. It's only an abstraction—a class that we made for convenience. But you could use it to whip up a Ferrari or a Geo Metro. This lesson has the details. They are interesting.

Let's talk about abstract classes in Java. Why are classes called "abstract"?

Let's dive deep into "access modifiers" and find out how they relate to the implementation of abstract methods and interfaces, as well as method overriding. Modifiers, like security guards, answer the question "Who can access this method/variable?" This lesson has the details.

All methods inside a class must have unique names. More specifically, the combination of a method's name and its set of parameter types must be unique. Imagine you need to write an Add() method to sum up two numbers. But you still aren't certain whether the numbers are ints or doubles. The smart thing to do is to overload the Add method. Rishi will explain everything else.