Random Test

import java.util.Random;
public class Book {
    public final Date creationDate;
    public String bookTitle;
    public static int bookCount;
    public Book(String bookTitle){
        this.bookTitle = bookTitle;
        this.creationDate = new Date();
    }
    public int randomID(){
        Random rand = new Random();
        int Id = rand.nextInt(10000);
        bookCount++;
        return Id;
    }
    public int getBookCount(){
        return bookCount;
    }
    public String toString(){
        return this.bookTitle;
    }

    public long shelfLife(){
        Date currentDate = new Date();
        long timeDiff = Math.abs(this.creationDate.getTime() - currentDate.getTime());
        return timeDiff;
    }

    public static void main(String[] args){
        Book book1 = new Book("book1");
        Book book2 = new Book("book2");
        System.out.println(book1.toString() + " id: " + book1.randomID());
        System.out.println(book2.toString() + " id: " + book2.randomID());
        System.out.println("book1 shelf life: " + book1.shelfLife() + " nanoseconds");
        System.out.println("bookcount: " + bookCount);    
        System.out.println(Book.bookCount);
        System.out.println(book1.bookCount);
    }
    }
Book.main(null);

book1 id: 3013
book2 id: 737
book1 shelf life: 11 nanoseconds
bookcount: 2
2
2

public class Novel extends Book{
    public String author;
    public Novel(String bookTitle){
        super(bookTitle);
    }

    public void Author(String author){
        this.author = author;
    }

    public String getAuthor(){
        return author;
    }
    
    public static void main(String args[]){
        Novel novel1 = new Novel("Novel One");
        System.out.println("novel1 shelf life: " + novel1.shelfLife() + " nanoseconds");
        System.out.println(novel1.toString());
    }
}
Novel.main(null);

novel1 shelf life: 0 nanoseconds
Novel One

public class Textbook extends Book{
    public String publishingCompany;
    public Textbook(String bookTitle){
        super(bookTitle);
    }

    public void publishingCompany(String publishingCompany){
        this.publishingCompany = publishingCompany;
    }

    public String getPublishingCompany(){
        return publishingCompany;
    }
    
    public static void main(String args[]){
        Textbook textbook1 = new Textbook("Textbook One");
        System.out.println("textbook1 shelf life: " + textbook1.shelfLife() + " nanoseconds");
        System.out.println(textbook1.toString());
    }
}
Textbook.main(null);

textbook1 shelf life: 0 nanoseconds
Textbook One