Congratulations on completing the Java OOP course! You've done a fantastic job making it this far! This course might have been short, but it was challenging. Object-oriented programming concepts are a crucial part of any programming language. The same programming concepts can be applied in other programming languages as well, as they remain consistent across languages, with only syntax differences.

Let's quickly recap what we've learned in this course:


Object-Oriented Programming (OOP) is a programming paradigm that focuses on organizing code around objects, which are instances of classes. OOP promotes concepts like encapsulation, inheritance, polymorphism, and abstraction to create modular, reusable, and maintainable code.

OOP concepts:


Inheritance is a fundamental concept in OOP where a new class can inherit attributes and behaviors from an existing class. This allows for code reuse and the creation of hierarchical relationships between classes. Inherited properties can be extended or overridden in the subclass.


Polymorphism enables objects of different classes to be treated as objects of a common superclass. This promotes flexibility and extensibility in code. Polymorphism is achieved through method overriding and method overloading.


Encapsulation involves bundling data (attributes) and methods (functions) that operate on the data into a single unit, called a class. Access to the data is controlled through methods, ensuring data integrity and hiding implementation details.

Abstraction focuses on presenting essential features of an object while hiding unnecessary details. It allows for the creation of abstract classes and interfaces that define a blueprint for subclasses. Abstraction helps in designing modular and loosely coupled systems.


These principles collectively enhance code organization, reusability, and maintainability, making OOP a powerful paradigm for software development. Each principle addresses specific aspects of designing and structuring classes and objects to create effective and efficient code.


Java interfaces are a fundamental concept in object-oriented programming that allows developers to define a contract for classes to adhere to. An interface serves as a blueprint for methods that must be implemented by classes that implement the interface. This promotes code reusability, maintainability, and multiple inheritance, as a class can implement multiple interfaces.

An interface in Java is like a blueprint for a class. It defines a set of methods that a class must implement. Think of it as a contract that a class agrees to follow. When a class implements an interface, it promises to provide specific functionality that the interface outlines. This allows different classes to share common methods without being tightly connected in terms of inheritance.

Abstract class vs Interface

Abstract class and interface serve very similar functions.

  • An abstract class is a class that provides some functionality and enforces certain rules but leaves some parts for its subclasses to complete;
  • An interface, on the other hand, is like a checklist that a class needs to fulfill, specifying what methods it must have, without providing any actual code. The illustration below highlights their main features:

And the most important conclusion - you're doing a fantastic job. I believe that you will succeed and get one step closer to mastering Java. This course might have been short but challenging. If you manage to grasp the concepts covered in this course, a bright future awaits you!


What programming paradigm must be used in Java

Select the correct answer

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Section 3. Chapter 6