Introduction to Object-Oriented Programming in Java: Learn Classes, Objects, Inheritance, Polymorphism, and OOP Concepts

1. What is Object-Oriented Programming (OOP)?

OOP is a programming paradigm based on the concept of "objects", which contain data (fields) and behavior (methods). Java is a fully object-oriented language that encourages clean and reusable code.

2. Key Concepts of OOP

OOP in Java is based on four main pillars:

• Encapsulation

• Inheritance

• Polymorphism

• Abstraction

These principles help in building applications that are modular, scalable, and easy to maintain.

3. Understanding Classes and Objects

• A class is a blueprint or template for creating objects.

• An object is an instance of a class.

Example: Basic Class and Object

public class Car {
    String color = "Red";
    int speed = 100;

    void drive() {
        System.out.println("Driving at " + speed + " km/h");
    }

    public static void main(String[] args) {
        Car myCar = new Car();  // Creating object
        System.out.println("Car Color: " + myCar.color);
        myCar.drive();
    }
}

Output:

Car Color: Red  
Driving at 100 km/h  

4. Encapsulation in Java

Encapsulation means hiding internal details and only exposing essential parts of an object via public methods.

Example: Encapsulation Using Getters and Setters

public class Person {
    private String name;

    public void setName(String n) {
        name = n;
    }

    public String getName() {
        return name;
    }

    public static void main(String[] args) {
        Person p = new Person();
        p.setName("Alice");
        System.out.println("Name: " + p.getName());
    }
}

5. Inheritance in Java

Inheritance allows one class to inherit properties and methods of another class using the extends keyword.

Example: Inheritance

class Animal {
    void sound() {
        System.out.println("This is a generic sound");
    }
}

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

public class TestInheritance {
    public static void main(String[] args) {
        Dog d = new Dog();
        d.sound();  // Inherited method
        d.bark();   // Dog's own method
    }
}

6. Polymorphism in Java

Polymorphism allows the same method to behave differently depending on the context. It can be:

• Compile-time (Method Overloading)

• Runtime (Method Overriding)

Example: Method Overriding

class Shape {
    void draw() {
        System.out.println("Drawing shape");
    }
}

class Circle extends Shape {
    void draw() {
        System.out.println("Drawing circle");
    }
}

public class TestPolymorphism {
    public static void main(String[] args) {
        Shape s = new Circle();  // Upcasting
        s.draw();  // Calls overridden method
    }
}

Output:

Drawing circle

7. Abstraction in Java

Abstraction hides complex implementation and shows only essential features. It is implemented using abstract classes or interfaces.

Example: Using Abstract Class

abstract class Animal {
    abstract void makeSound();
}

class Cat extends Animal {
    void makeSound() {
        System.out.println("Meow");
    }
}

public class TestAbstraction {
    public static void main(String[] args) {
        Animal a = new Cat();
        a.makeSound();
    }
}

Conclusion

Object-Oriented Programming in Java allows developers to build real-world, maintainable applications using principles like encapsulation, inheritance, polymorphism, and abstraction. Mastering OOP is crucial for professional Java development.

This Content Sponsored by Buymote Shopping app

BuyMote E-Shopping Application is One of the Online Shopping App

Now Available on Play Store & App Store (Buymote E-Shopping)

Click Below Link and Install Application: https://buymote.shop/links/0f5993744a9213079a6b53e8

Sponsor Content: #buymote #buymoteeshopping #buymoteonline #buymoteshopping #buymoteapplication