Classes & Objects

Java is an Object-Oriented language. Everything consists of classes and objects.

What is a Class?

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

public class Car {
    String color;
    String model;

    void drive() {
        System.out.println("Vroom vroom!");
    }
}

What is an Object?

An object is an instance of a class. If Car is the blueprint, then a specific red Ferrari is an object.

public class Main {
    public static void main(String[] args) {
        Car myCar = new Car(); // creating an object
        myCar.color = "Red";
        myCar.drive();
    }
}

Constructors

A constructor is a special method used to initialize objects. It is called when an object of a class is created.

• Name must match the class name.
• No return type (not even void).

public class Car {
    String model;

    // Constructor
    public Car(String modelName) {
        model = modelName;
    }

    public static void main(String[] args) {
        Car myCar = new Car("Tesla");
        System.out.println(myCar.model);
    }
}

Interactive Code

Design your own Dog class!

Quiz

Next Steps

Now that we have objects, let's learn the Four Pillars of OOP that make them powerful.