Adding user define class in Hastable in java

package addingcustomonjectinhashtable;
import java.util.*;


class Book {
	
	private String bookName;
	private int id;
	
	
	public Book(int id, String bookName) {
		super();
		this.id = id;
		this.bookName = bookName;
	}
	
	public String getBookName() {
		return bookName;
	}
	public void setBookName(String bookName) {
		this.bookName = bookName;
	}
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}


	
	
}
public class Example {
public static void main(String[] args) {
	Map<Book,String> hashtableObj = new Hashtable<>();
	Book b1 = new Book(2,"alchemist");
	Book b2 = new Book(3,"godan");
	Book b3 = new Book(4,"gaban");
	Book b4 = new Book(2,"mahabharta");
	Book b5 = new Book(2,"ramayana");
	hashtableObj.put(b1, "auther1");
	hashtableObj.put(b2, "auther2");
	hashtableObj.put(b3, "auther3");
	hashtableObj.put(b4, "auther4");
	hashtableObj.put(b5, "auther5");
	
	Set<Map.Entry<Book, String>> set = hashtableObj.entrySet();
	
	for(Map.Entry<Book, String> entry : set) {
		
		Book book = entry.getKey();
		String auther = entry.getValue();
		
		System.out.println("book id is "+book.getId() +" "+"book name is "+book.getBookName());
		System.out.println("auther is " +auther);
		
	}
	
}
}

Output is –

book id is 2 book name is alchemist
auther is auther1
book id is 2 book name is ramayana
auther is auther5
book id is 2 book name is mahabharta
auther is auther4
book id is 4 book name is gaban
auther is auther3
book id is 3 book name is godan
auther is auther2