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Exploring object-oriented programming concepts with Java
Object-Oriented Programming (OOP) is a programming paradigm that has been around for decades and is present in popular programming languages such as Java, Python, and C.
This method of structuring a program uses objects that have properties and behaviors. Java is a class-based, object-oriented programming language with a “write once, run anywhere” principle.
Today, we’ll learn about OOP concepts in Java. We’ll go over the basics of the syntax and the core concepts. By the end, you will be able to create classes and initialize Java objects which is important if you want to learn to code in Java.
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Overview of OOP in Java#
Object-oriented programming, also referred to as OOP, is a programming paradigm based on the concept of classes and objects. Objects have their own properties and behavior. A class is like a blueprint for creating objects.
In OOP, an object is defined with its own properties. For example, say our object is an Employee. These properties could be their name, age, and role. OOP makes it easy to model real-world things and the relationships between them.
In fact, objects in a program frequently represent real-world objects. Many beginners prefer to use OOP languages because they are more intuitive. OOP also helps to solve the problem of complexity by dividing the program into different objects.
The four main principles of OOP are inheritance, encapsulation, abstraction, and polymorphism. We’ll explore these more later using Java.
Check out our article What is Object Oriented Programming? for a refresher on these four principles before continuing here.
If you are familiar with Java programming, you must have noticed that whenever a program is written it is written inside a class, like the public class. Generally speaking, this class is referred to as the Main class. Even a basic program in Java is using classes, so Java is an OOP language.
What are OOP concepts in Java?#
The major advantage of the OOP framework in Java is that it lays the foundation for building modular, scalable, and efficient software. As noted earlier, the OOP programming paradigm emphasizes using objects to represent real-world concepts, with OOP meaning the use of classes and objects, inheritance, encapsulation, abstraction, and polymorphism to achieve this goal. We discuss more in detail below.
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Class and object: As previously highlighted, a class provides a template for object construction in Java. It includes all the objects’ properties and behaviors. An object is a specific representation of a class, containing all the properties and methods outlined within. Classes are by default static entities, while objects are more fluid and dynamic.
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Inheritance: Inheritance is a mechanism that allows a child class to inherit properties and methods from another class, also known as a superclass or parent class. The subclass/child class can then add its own properties and methods, or override the ones inherited from the superclass. This improves code reusability and aids in class hierarchy formation based on class connections.
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Encapsulation: Encapsulation is the practice of binding related data and the methods that manipulate it within a class. This method allows you to hide the implementation details of a class from the outside world, and only expose necessary details via a public interface for interacting with the object. This further ensures that only well-defined methods may access and modify the data, which helps to maintain data integrity and prevent unauthorized access.
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Abstraction: In Java, abstraction is a way of representing complex systems in a simplified form by hiding irrelevant details. Abstraction can be achieved through abstract classes and interfaces in Java.
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Polymorphism: Polymorphism in Java is when an object can have different forms, achieved through method overloading and overriding. Method overloading lets a class have multiple methods with the same name but distinct parameters. In contrast, method overriding allows a subclass to have its own unique method implementation inherited from the parent class.
The above section provided just a brief overview of key OOP concepts. The sections that follow will go deeper into each feature, providing a comprehensive understanding of how they can be used in software development.
Simple example of Java OOP#
We will explore this in more detail, but here’s a simple example to get you started. The following code creates different Dog objects and stores them.
public class Dog {};
Dog GermanShephered = new Dog();
Dog Bulldog = new Dog();
Dog Labrador = new Dog();