Super keyword in Java - Mini Project: Build & Apply

Understanding the Super Keyword in Java

📖 Scenario: Imagine you are creating a simple program to represent vehicles. You have a basic Vehicle class and a more specific Car class that inherits from Vehicle. You want to use the super keyword to access the parent class's constructor and methods.

🎯 Goal: You will build two classes: Vehicle and Car. You will use the super keyword to call the parent class constructor and method from the child class. Finally, you will print the details of the car using these calls.

📋 What You'll Learn

Create a class called Vehicle with a constructor that takes a String parameter called brand and stores it in an instance variable.

Create a method in Vehicle called displayInfo() that prints the vehicle brand.

Create a class called Car that extends Vehicle and has an additional instance variable model.

Use the super keyword in Car's constructor to call the Vehicle constructor.

Override the displayInfo() method in Car and use super.displayInfo() to print the brand before printing the model.

Create an instance of Car and call its displayInfo() method to show the output.

💡 Why This Matters

🌍 Real World

Using <code>super</code> is common when you want to build new classes based on existing ones, like creating different types of vehicles or employees with shared and unique features.

💼 Career

Understanding inheritance and the <code>super</code> keyword is essential for Java developers to write clean, reusable, and maintainable code in many software projects.

1

Create the Vehicle class with a brand variable and constructor

Create a class called Vehicle with a String instance variable called brand. Add a constructor that takes a String brand parameter and assigns it to the instance variable brand.

Java

class Vehicle {
    // Your code here
}

Need a hint?

Remember to create a constructor with the same name as the class and assign the parameter to the instance variable.

2

Add a displayInfo() method to Vehicle

Inside the Vehicle class, add a method called displayInfo() that prints the text "Vehicle brand: " followed by the brand variable.

Java

class Vehicle {
    String brand;

    Vehicle(String brand) {
        this.brand = brand;
    }

    // Your code here
}

Need a hint?

Use System.out.println to print the brand with the label.

3

Create the Car class that extends Vehicle with a model variable

Create a class called Car that extends Vehicle. Add a String instance variable called model. Create a constructor for Car that takes two String parameters: brand and model. Use the super keyword to call the Vehicle constructor with brand, and assign model to the instance variable.

Java

class Vehicle {
    String brand;

    Vehicle(String brand) {
        this.brand = brand;
    }

    void displayInfo() {
        System.out.println("Vehicle brand: " + brand);
    }
}

// Your code here

Need a hint?

Use super(brand); inside the Car constructor to call the parent constructor.

4

Override displayInfo() in Car and print brand and model

In the Car class, override the displayInfo() method. Inside it, first call super.displayInfo() to print the brand. Then print "Car model: " followed by the model variable. Finally, create a Car object with brand "Toyota" and model "Corolla", and call its displayInfo() method.

Java

class Vehicle {
    String brand;

    Vehicle(String brand) {
        this.brand = brand;
    }

    void displayInfo() {
        System.out.println("Vehicle brand: " + brand);
    }
}

class Car extends Vehicle {
    String model;

    Car(String brand, String model) {
        super(brand);
        this.model = model;
    }

    // Your code here
}

// Create a Car object and call displayInfo()
// Your code here

Need a hint?

Use super.displayInfo(); to reuse the parent method, then print the model. Create the Car object and call displayInfo() in the main method.