Default constructor in Java - Mini Project: Build & Apply

Default constructor

📖 Scenario: Imagine you are creating a simple program to represent a book in a library. Each book has a title and an author. Sometimes, you want to create a book without giving any details first, and then add details later.

🎯 Goal: You will create a Book class with a default constructor that sets the title and author to default values. Then, you will create an object of this class and print its details.

📋 What You'll Learn

Create a class called Book

Add a default constructor to Book that sets title to "Unknown Title" and author to "Unknown Author"

Create an object of Book using the default constructor

Print the title and author of the created Book object

💡 Why This Matters

🌍 Real World

Default constructors are used to create objects with default settings before setting specific details later.

💼 Career

Understanding constructors is essential for creating and initializing objects in Java, a key skill for software development.

1

Create the Book class with title and author fields

Create a class called Book with two String fields: title and author.

Java

public class Book {
    // Your code here
}

Need a hint?

Fields are variables inside a class. Use String title; and String author; inside the class.

2

Add a default constructor to Book

Add a default constructor to the Book class that sets title to "Unknown Title" and author to "Unknown Author".

Java

public class Book {
    String title;
    String author;

    // Your code here
}

Need a hint?

A default constructor has no parameters and sets the fields inside its body.

3

Create a Book object using the default constructor

In a Main class, create a Book object called myBook using the default constructor.

Java

public class Book {
    String title;
    String author;

    public Book() {
        title = "Unknown Title";
        author = "Unknown Author";
    }
}

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

Need a hint?

Use Book myBook = new Book(); to create the object.

4

Print the title and author of the Book object

In the main method, print the title and author of the myBook object using System.out.println.

Java

public class Book {
    String title;
    String author;

    public Book() {
        title = "Unknown Title";
        author = "Unknown Author";
    }
}

public class Main {
    public static void main(String[] args) {
        Book myBook = new Book();
        // Your code here
    }
}

Need a hint?

Use System.out.println(myBook.title); and System.out.println(myBook.author); to print the values.