Creating a Java Book Class with Encapsulation and Discount Method

Java Encapsulatiion: Exercise-8 with Solution

Write a Java program to create a class called “Book” with private instance variables title, author, and price. Provide public getter and setter methods to access and modify these variables. Add a method called applyDiscount() that takes a percentage as a parameter and reduces the price by that percentage.

Sample Solution:

Java Code:

Book.java

// Define the Book class
public class Book {
    // Private instance variables
    private String title;
    private String author;
    private double price;

    // Public getter for the title variable
    public String getTitle() {
        return title;
    }

    // Public setter for the title variable
    public void setTitle(String title) {
        this.title = title;
    }

    // Public getter for the author variable
    public String getAuthor() {
        return author;
    }

    // Public setter for the author variable
    public void setAuthor(String author) {
        this.author = author;
    }

    // Public getter for the price variable
    public double getPrice() {
        return price;
    }

    // Public setter for the price variable
    public void setPrice(double price) {
        this.price = price;
    }

    // Method to apply a discount to the price
    public void applyDiscount(double percentage) {
        if (percentage > 0 && percentage <= 100) {
            this.price -= this.price * (percentage / 100);
        }
    }
 }

Main.java

// Main method to test the Book class
 public class Main {
    public static void main(String[] args) {
        // Create a new Book object
        Book book = new Book();

        // Set the title, author, and price of the book
        book.setTitle("Java Programming");
        book.setAuthor("Imani Matey");
        book.setPrice(35.0);

        // Apply a 10% discount to the book price
        book.applyDiscount(10);

        // Print the details of the book
        System.out.println("Title: " + book.getTitle());
        System.out.println("Author: " + book.getAuthor());
        System.out.println("Price: $" + book.getPrice());
    }
 }

Output:

Title: Java Programming
Author: Imani Matey
Price: $31.5

Explanation:

• Private Instance Variables: The title, author, and price variables are declared as private to ensure encapsulation.
• Public Getters and Setters: These methods provide controlled access to the private variables.
• getTitle(): Returns the title.
• setTitle(String title): Sets the title.
• getAuthor(): Returns the author.
• setAuthor(String author): Sets the author.
• getPrice(): Returns the price.
• setPrice(double price): Sets the price.
• applyDiscount Method: Takes a percentage and reduces the price by that percentage.
• Main Method: Tests the functionality of the Book class by creating an instance, setting its properties, applying a discount, and printing the details.

Note on Encapsulation

Encapsulation works in the above exercise by:

• Hiding Data: The private instance variables title, author, and price are not accessible directly from outside the class.
• Controlled Access: The public getter and setter methods provide controlled access to the private variables, allowing for validation and modification when necessary.
• Data Integrity: Encapsulation helps maintain data integrity by ensuring that the internal state of the object can only be changed through well-defined methods.

Java Code Editor:

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