Java OOP: Class and Object

Java OOP Concepts: Class and Object (Beginner Guide with Examples)

✨ Quick Summary

In this post, you’ll learn the basics of Object-Oriented Programming (OOP) in Java. We will cover what a Class is, what an Object is, how to create them, and understand OOP with simple real-life examples.

Java OOP Class Object

In our previous post, we learned about Java Methods and how to create reusable code.

Now it’s time to start the most important part of Java: Object-Oriented Programming (OOP).

Java is an OOP-based language, which means Java programs are built using:

• ✅ Classes
• ✅ Objects
• ✅ Methods
• ✅ Inheritance, Polymorphism, Encapsulation, Abstraction

In this post, we will start with the basics: Class and Object.

---

1) What is a Class?

A Class is like a blueprint or template. It defines what an object will have.

Example: A class is like a blueprint of a Car. The blueprint contains:

• Car name
• Car color
• Car model
• Car speed

But the blueprint is not a real car. It is just the design.

---

2) What is an Object?

An Object is the real thing created from a class.

Example: If class is Car, then objects can be:

• BMW
• Audi
• Tata

---

3) Example: Create a Class and Object in Java

class Student {

    String name;
    int age;

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

public class ClassObjectExample {
    public static void main(String[] args) {

        Student s1 = new Student();

        s1.name = "Aishwarya";
        s1.age = 22;

        s1.display();
    }
}

---

4) Multiple Objects Example

You can create multiple objects from the same class.

class Car {

    String brand;
    String color;

    void showCar() {
        System.out.println("Brand: " + brand);
        System.out.println("Color: " + color);
    }
}

public class MultipleObjectsExample {
    public static void main(String[] args) {

        Car c1 = new Car();
        c1.brand = "BMW";
        c1.color = "Black";

        Car c2 = new Car();
        c2.brand = "Tata";
        c2.color = "White";

        c1.showCar();
        System.out.println("-----");
        c2.showCar();
    }
}

---

5) Constructor (Introduction)

A Constructor is a special method used to initialize objects.

Constructor name is always the same as class name.

Example:

class Student {

    Student() {
        System.out.println("Constructor called!");
    }
}

We will learn constructors in detail in the next post.

---

Conclusion

Class and Object are the foundation of Java OOP. Once you understand this, you can easily learn:

• ✅ Constructors
• ✅ Inheritance
• ✅ Polymorphism
• ✅ Encapsulation
• ✅ Abstraction

In the next post, we will learn about Java Constructors in detail with examples!