Parent and child classes in Java - Mini Project: Build & Apply

Parent and Child Classes

📖 Scenario: You are creating a simple program to represent vehicles. You want to show how a child class can inherit properties from a parent class.

🎯 Goal: Build a parent class called Vehicle and a child class called Car that inherits from Vehicle. Then create an object of Car and print its details.

📋 What You'll Learn

Create a parent class named Vehicle with a String field called brand.

Create a child class named Car that extends Vehicle and adds an int field called year.

Create a constructor in Vehicle to set the brand.

Create a constructor in Car to set both brand and year.

Create a method displayInfo() in Car that prints the brand and year.

Create a Car object with brand "Toyota" and year 2020, then call displayInfo().

💡 Why This Matters

🌍 Real World

Understanding parent and child classes helps organize code by sharing common features and adding specific details, like different types of vehicles.

💼 Career

Inheritance is a key concept in object-oriented programming used in many software development jobs to build reusable and maintainable code.

1

Create the parent class Vehicle

Create a public class called Vehicle with a String field named brand. Add a constructor that takes a String brand parameter and sets the field.

Java

public class Vehicle {
    // Your code here
}

Need a hint?

Think of Vehicle as a blueprint with a brand name. The constructor sets the brand.

2

Create the child class Car

Create a public class called Car that extends Vehicle. Add an int field named year. Create a constructor that takes String brand and int year parameters. Use super(brand) to call the parent constructor and set year.

Java

public class Vehicle {
    String brand;

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

// Your code here

Need a hint?

Use extends to inherit from Vehicle. Use super to call the parent constructor.

3

Add displayInfo method in Car

Inside the Car class, create a public method called displayInfo() that prints the brand and year in this format: "Brand: [brand], Year: [year]".

Java

public class Vehicle {
    String brand;

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

public class Car extends Vehicle {
    int year;

    public Car(String brand, int year) {
        super(brand);
        this.year = year;
    }

    // Create displayInfo method here
    // Your code here
}

Need a hint?

Use System.out.println to print the message. Access brand directly because it is inherited.

4

Create Car object and print info

In a public class called Main, create the main method. Inside it, create a Car object with brand "Toyota" and year 2020. Call the displayInfo() method on this object to print the details.

Java

public class Vehicle {
    String brand;

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

public class Car extends Vehicle {
    int year;

    public Car(String brand, int year) {
        super(brand);
        this.year = year;
    }

    public void displayInfo() {
        System.out.println("Brand: " + brand + ", Year: " + year);
    }
}

// Your code here

Need a hint?

Remember the main method signature and how to create objects with new.