Java OOP Concepts for Beginners: A Guide to Object-Oriented Programming

Introduction

Object-Oriented Programming(OOP) is a basic style of programming. Java is the first name that comes to mind when talking about programming languages that are object-oriented and scalable code. If you are a beginner or already know programming but want to learn Java as well, then having an understanding of its OOP concepts is necessary for becoming good at Java coding.

In this Java OOPS, we will learn about pillars of Java object oriented programming, such as Classes, Objects, Inheritance Polymorphism, Encapsulation, and Abstraction. After this blog, you will already get a solid ground to proceed in Java programming.

What is Object-Oriented Programming?

Object-Oriented Programming (OOP) is a programming paradigm based on the concept of "objects", which can contain data in the form of fields (attributes or properties) and code in the form of procedures (methods). Key principles of OOP include encapsulation, inheritance, polymorphism, and abstraction.

What are the main principles of OOP?

1. Encapsulation: Bundling the data (attributes) and methods (functions) that operate on the data into a single unit called a class. It restricts direct access to some of the object's components.

2. Inheritance: A mechanism where one class (child/subclass) can inherit fields and methods from another class (parent/ superclass).

3. Polymorphism: The ability of different classes to be treated as instances of the same class through inheritance. It allows methods to be defined in multiple forms.

4. Abstraction: Hiding the complex implementation details and showing only the necessary features of an object.

What is a Class in Java?

A class is a blueprint for creating objects. It defines a datatype by bundling data and methods that work on the data into one single unit.

For example:

public class Person {
    String name;
    int age;
    public void displayDetails() {
        System.out.println("Name: " + name);
        System.out.println("Age: " + age);
    }
}

What is an Object in Java?

An object is an instance of a class. It is created using the new keyword.

For example:

Person newPerson = new Person();

Here newPerson is an object of the class Person.

What is Inheritance in Java?

Inheritance is a mechanism where a new class (subclass) inherits the properties and behavior (fields and methods) of another class (superclass).

For example:

class Student {
    String studentId;
}

class Student extends Person {
    String studentAddress;
}

What is Polymorphism in Java?

Polymorphism allows methods to do different things based on the object it is acting upon. It can be achieved through method overriding (runtime polymorphism) and method overloading (compile-time polymorphism).

For example.

class Animal {
    public void sound() {
        System.out.println("Animal makes a sound");
    }
}

class Dog extends Animal {
    public void sound() {
        System.out.println("Dog barks");
    }
}

// MAIN METHOD
public class TestPolymorphism {
    public static void main(String[] args) {
        Animal a = new Dog();
        a.sound(); // Outputs "Dog barks"
    }
}

What is Encapsulation in Java?

Encapsulation is the technique of making the fields (attributes) in a class private and providing access to the fields via public methods. This helps protect the data and allows controlled access to it.

For example.

public class Person {
    private String name;

    public void setName(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }
}

What is an Abstraction in Java?

Abstraction is the concept of hiding the complex implementation details and showing only the essential features of the object. It can be achieved using abstract classes and interfaces.

For example.

abstract class Animal() {
    abstract void makeSound();
}

class Dog extends Animal {
    void makeSound() {
        System.out.println("Bark");
    }
}

Conclusion

Getting hands dirty on object-oriented programming concepts in Java is the main stepping stone for any programmer who wants to become an expert Java developer. Classes and objects, inheritance, polymorphism, encapsulation, and abstraction are the main principles behind Java that help in writing efficient code that is easy to maintain.

This provides the ability to solve complex problems in the elegant way, make a reusable component, and also scaling of your application can be done. The more you practice and build projects, the more details about these OOP principles will become second nature to help you concentrate on real-world problems instead of focusing on coding structure. Keep practicing, coding, and enhancing your skills, you will eventually realize the OOP power of JAVA.