UniqueBookSetDemo.java

import java.util.HashSet;
import java.util.Objects;

// 1. The Book Class
class Book {
    private String title;
    private String author;

    public Book(String title, String author) {
        this.title = title;
        this.author = author;
    }

    // Overriding equals() to ensure equality is based purely on title and author
    @Override
    public boolean equals(Object obj) {
        if (this == obj) return true;
        if (obj == null || getClass() != obj.getClass()) return false;
        
        Book book = (Book) obj;
        return title.equals(book.title) && author.equals(book.author);
    }

    // Overriding hashCode() to maintain the Java contract with equals()
    @Override
    public int hashCode() {
        return Objects.hash(title, author);
    }

    public void display() {
        System.out.println("\nTitle: " + title);
        System.out.println("Author: " + author);
    }
}

// 2. Main Driver Class (PascalCase)
public class UniqueBookSetDemo {
    public static void main(String[] args) {
        // Initialize the HashSet to store only unique Book objects
        HashSet<Book> books = new HashSet<>();

        System.out.println("--- Adding Books to the Library ---");

        // Adding unique books
        books.add(new Book("The Lord of the Rings", "J.R.R. Tolkien"));
        books.add(new Book("Pride and Prejudice", "Jane Austen"));
        books.add(new Book("To Kill a Mockingbird", "Harper Lee"));

        // Adding duplicate books (These will be automatically ignored by the HashSet!)
        books.add(new Book("The Lord of the Rings", "J.R.R. Tolkien")); // Duplicate
        books.add(new Book("Pride and Prejudice", "Jane Austen"));      // Duplicate

        System.out.println("Books processed! Duplicates have been filtered out.");
        System.out.println("\n--- Unique Books in the Set ---");
        
        // Iterate through the HashSet and print the unique books
        for (Book book : books) {
            book.display();
        }
        
        System.out.println("\n-------------------------------");
    }
}