Understanding Object-Oriented Programming (OOP) in Java ( Abstraction | Encapsulation | Inheritance | Polymorphism )

Hi, Welcome all. In this blog post, we are going to learn the basics of OOP (Object Oriented Programming ) in Java and how it can be used to create a robust and scalable application.

Object Oriented Programming (OOP) is a programming paradigm that focuses on creating objects that interact with each other to solve complex problems. Java is used extensively for developing applications, and it is also an excellent language for practicing OOP concepts. In this article, we will discuss the 4 Pillars of OOP in Java and how it can be used to create robust and scalable applications.

What is Object-Oriented Programming (OOP)?

Before understanding the 4 pillars of OOP, let first understand what is Object-Oriented Programming (OOP)?

Object-oriented programming is a programming paradigm that revolves around the concept of objects. An object is a real-world entity that has properties and behavior. For example, a car is an object that has properties such as color, model, and behavior such as starting, stopping, and accelerating.

In OOP, you define objects and their relationship with each other to create a modular and flexible application structure. This makes it easier to manage the application and add new features to it in the future. OOP is based on four main principles: Encapsulation, Inheritance, Abstraction, and Polymorphism.

Four Main Principals of OOP

1. Abstraction.
2. Encapsulation.
3. Inheritance
4. Polymorphism.

1. Abstraction: 

   Abstraction is a fundamental concept in object-oriented programming that allows you to create complex systems by breaking them down into smaller, more manageable components. In Java, abstraction is achieved using two main mechanisms: abstract classes and interfaces.

In Java, you can define an abstract class using the abstract keyword. Here's an example of how to define an abstract class:

In the example above, the Animal class is declared as abstract using the abstract keyword. It contains one abstract method makeSound(), which is declared without an implementation using the abstract keyword. This method will be implemented in the concrete subclasses that extend the Animal class.

The Animal class also contains a concrete method eat(), which has an implementation. This method will be inherited by any subclasses that extend the Animal class.

Note that you cannot create an instance of an abstract class. (means we cannot create abstract class object) To use the Animal class, you must create a concrete subclass that extends it and provide an implementation for the makeSound() method:

How to Use an Abstract Class?

To use an abstract class in Java, you must create a concrete subclass that extends the abstract class and provides an implementation for any abstract methods. Here's an example of a concrete subclass called Dog that extends the Animal class:

In this example, the Dog class extends the Animal class and provides an implementation for the makeSound() method by printing "Woof!" to the console. The Dog class can also inherit the sleep() method from the Animal class.

Conclusion

Abstract classes are a powerful tool for improving the design and organization of your code. They allow you to define a common interface for a group of related classes, promote code reusability and modularity, and provide a set of default behaviors that can be inherited by subclasses. By understanding how to use abstract classes in Java, you can create more efficient and effective applications that are easier to maintain and update.

2. Encapsulation

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