Instance variables in Java - Mini Project: Build & Apply

Instance variables

📖 Scenario: Imagine you are creating a simple program to keep track of a book's details in a library system. Each book has a title and an author.

🎯 Goal: You will create a class called Book with instance variables to store the title and author. Then, you will create an object of this class and print its details.

📋 What You'll Learn

Create a class called Book

Add instance variables title and author of type String

Create an object of Book with title "The Alchemist" and author "Paulo Coelho"

Print the book's title and author using the object

💡 Why This Matters

🌍 Real World

Instance variables are used to store information about objects in real-world programs, like details of books, students, or products.

💼 Career

Understanding instance variables is essential for object-oriented programming, which is widely used in software development jobs.

1

Create the Book class with instance variables

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

Java

public class Book {
    // Your code here
}

Need a hint?

Instance variables are declared inside the class but outside any method.

2

Create a Book object with specific title and author

In the Main class, create a Book object called myBook. Set its title to "The Alchemist" and author to "Paulo Coelho".

Java

public class Book {
    String title;
    String author;
}

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

Need a hint?

Create the object using new Book() and assign values to instance variables using the dot . operator.

3

Print the book's title and author

Use System.out.println to print the book's title and author from the myBook object. Print the title first, then the author on the next line.

Java

public class Book {
    String title;
    String author;
}

public class Main {
    public static void main(String[] args) {
        Book myBook = new Book();
        myBook.title = "The Alchemist";
        myBook.author = "Paulo Coelho";
        // Your code here
    }
}

Need a hint?

Use System.out.println twice, once for the title and once for the author.

4

Run the program to see the output

Run the program to display the book's title and author on the screen.

Java

public class Book {
    String title;
    String author;
}

public class Main {
    public static void main(String[] args) {
        Book myBook = new Book();
        myBook.title = "The Alchemist";
        myBook.author = "Paulo Coelho";
        System.out.println(myBook.title);
        System.out.println(myBook.author);
        // Your code here
    }
}

Need a hint?

The program should print the title and author on separate lines.