Class and Object in Java – A Complete Beginner’s Guide

In Java, Object-Oriented Programming (OOP) plays a crucial role in structuring applications using real-world concepts. The two most fundamental concepts of OOP are Class and Object. Understanding these is essential for every Java developer.

✅ What is a Class in Java?

A Class is a blueprint or template for creating objects. It defines the properties (attributes or fields) and behaviors (methods) that the objects created from the class will have.

🔍 Key Points About Class:

• Acts like a template.
• Defines fields (variables) and methods (functions).
• Does not consume memory directly.

✅ Class Syntax Example:

public class Car {
    // Fields (Properties)
    String color;
    String model;
    int year;

    // Method (Behavior)
    public void displayDetails() {
        System.out.println("Model: " + model);
        System.out.println("Color: " + color);
        System.out.println("Year: " + year);
    }
}

✅ What is an Object in Java?

An Object is an instance of a class. It occupies memory and holds actual values for the fields defined in the class. Through the object, you can access the methods and variables defined in the class.

✅ Object Creation Example:

public class Main {
    public static void main(String[] args) {
        // Creating an object of the Car class
        Car myCar = new Car();

        // Assign values to the fields
        myCar.model = "Toyota Camry";
        myCar.color = "Red";
        myCar.year = 2022;

        // Call method using the object
        myCar.displayDetails();
    }
}

✅ Output:

Model: Toyota Camry
Color: Red
Year: 2022

✅ Class vs Object – Quick Comparison

✅ Why Use Class and Object?

• Encapsulation: Organizes data and behavior in one unit.
• Reusability: Once the class is created, multiple objects can be created and reused.
• Abstraction: Internal implementation is hidden; you interact only via methods.
• Real-World Representation: Classes represent real-world entities, making it easy to model complex problems.

✅ Example With Multiple Objects

public class Main {
    public static void main(String[] args) {
        Car car1 = new Car();
        car1.model = "Honda Civic";
        car1.color = "Blue";
        car1.year = 2020;

        Car car2 = new Car();
        car2.model = "Ford Mustang";
        car2.color = "Black";
        car2.year = 2021;

        System.out.println("Car 1 Details:");
        car1.displayDetails();

        System.out.println("\nCar 2 Details:");
        car2.displayDetails();
    }
}

✅ Key Concepts to Remember

• A class defines what an object will look like and what it can do.
• An object is a real instance of the class that holds actual values and can perform actions (methods).
• You can create multiple objects from the same class, each with its own state.

✅ Conclusion

Understanding Class and Object is the first step toward mastering Java’s object-oriented programming. It allows you to model real-world entities and perform structured programming with easy code reusability and better maintainability.