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Hi! In today's lesson, we'll get acquainted with the concept of access modifiers and consider examples of how to work with them. Of course, saying 'get acquainted' isn't quite right: you are already familiar with most of them from previous lessons. Just in case, let's refresh our memory of the most important...

Hi! In a past lesson, we discussed casting primitive types. Let's briefly recall what was discussed. We imagined primitive types (in this case, numeric types) as nesting dolls that vary in size according to the amount of memory they occupy...

While CodeGym is busy creating the next big content release, what would you suggest as a next step? My goal is to learn enough Java that I can start working as a Jr. Developer. I've been at this for almost a year now, going through online "Learn Java" programs, reading through several of the top recommended books...

Hi! Today we'll talk about the instanceof operator, consider examples of how it is used, and touch on some aspects of how it works:) You've already encountered this operator on early levels of CodeGym. Do you remember why we need it? If not, no worries. Let's remember together...

Hi! In this lesson, we'll talk about how abstract classes differ from interfaces and consider some examples with common abstract classes. We've devoted a separate lesson to the differences between an abstract class and an interface, because this topic is very important...

Hi! In past lessons, we met interfaces and figured out what they're for. Today's topic will echo the previous one. Let's talk about abstract classes in Java. You probably remember what 'abstraction' is — we've already gone over it. :) If you forgot, fear not. Remember: it's a principle of OOP...

Every new version of Java differs from those that came before. Here's an example of changes in material that we've covered: before Java 5, the language didn't have enums. Similarly, Java 8 differs markedly from Java 7. Most of our lessons were written for the 7th version of the language...

Hi! Today we're going to talk about an important concept in Java: interfaces.The word is probably familiar to you. For example, most computer programs and games have interfaces. In a broad sense, an interface is a kind of 'remote control' that connects two interacting parties...

Hi! You're already using Java methods and know a lot about them. You've probably faced the situation where one class has many methods with the same name but different parameters. You'll recall that in those cases we used method overloading. Today we're considering another situation ...

Hi! Today we conclude a series of lessons on the principles of OOP. In this lesson, we'll talk about polymorphism. Polymorphism is the ability to work with several types as if they were the same type. Moreover, the objects' behavior will be different depending on their type ...

Hi! We'll devote today's lesson to encapsulation and begin with examples right out of the gate:) Here you have an ordinary soda dispensing machine. I've got one question for you: how does it work? Try to give a detailed answer: Where does the soda come from? How is the internal temperature maintained?

Hi! Today we'll take a closer look at one principle of Object Oriented Programming (OOP): Inheritance. We'll also study other types of relationships between classes: composition and aggregation ...