Java OOP Concepts Explained Simply: Class, Object, Inheritance, Polymorphism

Java OOP Concepts Explained Simply

Author: Gursehbaj Singh | Blog: DevMode

Object-Oriented Programming (OOP) is the heart of Java. It helps us create real-world programs using objects and classes. In this post, you will learn all main OOP concepts in a simple and clear way.

What is OOP?

OOP is a programming style where everything is represented as objects. Each object has data and behavior.

1. Class

A class is a blueprint of an object.

class Student {
    String name;
    int age;

    void display() {
        System.out.println(name + " " + age);
    }
}

2. Object

An object is created from a class.

Student s1 = new Student();
s1.name = "Gursehbaj";
s1.age = 18;
s1.display();

3. Inheritance

Inheritance allows one class to use properties of another class.

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

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

4. Polymorphism

Polymorphism means many forms.

class Calculator {
    int add(int a, int b) {
        return a + b;
    }

    int add(int a, int b, int c) {
        return a + b + c;
    }
}

5. Encapsulation

Encapsulation means wrapping data with methods.

class Account {
    private int balance;

    public void setBalance(int b) {
        balance = b;
    }

    public int getBalance() {
        return balance;
    }
}

6. Abstraction

Abstraction means hiding internal details.

abstract class Shape {
    abstract void draw();
}

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

Why OOP is Important?

• Code reusability
• Easy maintenance
• Better security
• Real-world modeling

Conclusion

OOP makes Java powerful and flexible. By learning class, object, inheritance, polymorphism, encapsulation and abstraction, you can build large and professional applications easily.