Abstract classes in Java - Mini Project: Build & Apply

Using Abstract Classes in Java

📖 Scenario: You are creating a simple program to represent different types of vehicles. Each vehicle has a method to display its sound. You want to use an abstract class to define the common structure for all vehicles.

🎯 Goal: Build a Java program that uses an abstract class called Vehicle with an abstract method makeSound(). Then create two subclasses Car and Bike that provide their own implementation of makeSound(). Finally, create objects of these subclasses and call their makeSound() methods.

📋 What You'll Learn

Create an abstract class called Vehicle with an abstract method makeSound().

Create a class Car that extends Vehicle and implements makeSound() to print "Car goes vroom".

Create a class Bike that extends Vehicle and implements makeSound() to print "Bike goes ring ring".

In the Main class, create one Car object and one Bike object.

Call the makeSound() method on both objects and print the results.

💡 Why This Matters

🌍 Real World

Abstract classes help organize code when many objects share common features but have different specific behaviors, like different types of vehicles.

💼 Career

Understanding abstract classes is important for designing flexible and reusable code in many software development jobs.

1

Create the abstract class Vehicle

Create an abstract class called Vehicle with an abstract method makeSound() that returns void.

Java

abstract class Vehicle {
    // Your code here
}

Need a hint?

Use the keyword abstract before the class and method. The method has no body.

2

Create the Car and Bike classes

Create a class called Car that extends Vehicle and implements the makeSound() method to print "Car goes vroom". Also create a class called Bike that extends Vehicle and implements the makeSound() method to print "Bike goes ring ring".

Java

abstract class Vehicle {
    abstract void makeSound();
}

// Your code here

Need a hint?

Remember to use extends Vehicle and override the makeSound() method with void makeSound().

3

Create objects of Car and Bike

Create a class called Main with a main method. Inside the main method, create one object of Car called myCar and one object of Bike called myBike.

Java

abstract class Vehicle {
    abstract void makeSound();
}

class Car extends Vehicle {
    void makeSound() {
        System.out.println("Car goes vroom");
    }
}

class Bike extends Vehicle {
    void makeSound() {
        System.out.println("Bike goes ring ring");
    }
}

class Main {
    public static void main(String[] args) {
        // Your code here
    }
}

Need a hint?

Use new Car() and new Bike() to create the objects inside the main method.

4

Call makeSound() on the objects and print output

In the main method of the Main class, call the makeSound() method on the myCar and myBike objects to print their sounds.

Java

abstract class Vehicle {
    abstract void makeSound();
}

class Car extends Vehicle {
    void makeSound() {
        System.out.println("Car goes vroom");
    }
}

class Bike extends Vehicle {
    void makeSound() {
        System.out.println("Bike goes ring ring");
    }
}

class Main {
    public static void main(String[] args) {
        Car myCar = new Car();
        Bike myBike = new Bike();
        // Your code here
    }
}

Need a hint?

Call myCar.makeSound() and myBike.makeSound() to print the sounds.