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Congratulations, this marks the beginning of the second quest! You will learn the basics of OOP, streams, and serialization. You'll learn about method overloading, interfaces and multiple inheritance. Regular practice (by completing tasks) will help you pass all 10 levels in this quest and you'll soon be ready to complete mini-projects.

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.

The last two lessons have prepared you to dive deeper into the essence of OOP. Professor Noodles isn't wasting any time. He's found one of the best articles on OOP for you. It's super interesting, but rather long and highly detailed. If something in it seems difficult, don't worry about it for now.

Once upon a time there was horse. It nibbled the grass, galloped around, and lived in peace. Then a programmer came along, and suddenly the horse had a descendent — Pegasus, a winged horse. This new beast inspired others to take on multiple jobs. It was like a horse: it knew how to nibble grass and gallop. But it also knew how to fly. This is how subclasses appeared in Java. The details are in the lesson.

Wanna build an off-road vehicle from old VW Beetles? Slap some wings on a horse? Bolt an umbrella onto a fish? No problem! Java, OOP, and inheritance are at your disposal. We'll tackle some "inheritance" tasks without forgetting common sense.

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.

It's time for some practice. This time you need to complete a handful of tasks about OOP and encapsulation. You'll need to work on instances variables and methods that can change objects' internal state.

You've probably already guessed that Professor Hans Noodles doesn't give bad advice! This time he's found a link to an excellent lesson about inheritance and encapsulation. It will help you add some structure to your knowledge, if you want to.

Resting is useful! And resting in a useful way is even more useful. It's time to relax a bit, watch a cool video... and get a bunch of dark matter for it! Videos about technology and famous nerds are an excellent substitute for TV shows. This time we suggest that you watch a documentary about Elon Musk.

Another small peak can be seen on the horizon: the end of the second quest is getting close! All you need to do is solidify your new knowledge about inheritance and encapsulation, and then expand what you know by completing some bonus tasks.