Stuck with Java Objected Orientated Programming - Array

[Phalanx]

Hey, I stumbled upon this forum on google and people seem to be very helpful, so I thought I'd post my problem (ethical or unethical?)

I've been going through my coursework and I just can't get my head around using Arrays in a class. I'll post the question followed by the code.

1. Create a new class called BookStore. Your shop will have two fields, an array storing a collection of books (Book[] anyname) and an integer for the number of books in the collection.

Add a constructor which initialises the field variables appropriately. (Here you should construct an empty array object, where you can determine the size).

The question after this is:

2. Write a method addBook that takes a Book object as parameter and puts it in the next free space in the collection. What should you do with the field variable for the number of existing books?

Well, I think I've done 1. fine, but I'm not sure about two, I just can't get my head around "Book" as an object. I understand the last part, I should reduce the number of existing books.

I'll post my code for the Bookstore class and the Book class.

public class BookStore
{
    Book[] stock;
    int NoOfBooks;

    public void initiliaseArray (int NoOfBooks)
    {
        NoOfBooks = NoOfBooks;
        stock = new Book[NoOfBooks];
    }
    
    public void addBook (Book)
    {
    }


}

public class Book
{
    
private String author;
private String title;
private int year;
private double price;
private double pricespecial = 0;

    public Book ()
    { }
    

    public void getauthor(String authorhold)
    {
        author = authorhold;
    }
    
    public void gettitle(String titlehold)
    {
        title = titlehold;
    }
    
    public int getyear(int yearhold)
    {
        year = yearhold;
        return year;
    }
    
    public double getprice(double pricehold)
    {
       price = pricehold;
       return price; 
    }
    
    public void reduceprice (double percentage)
    {
        pricespecial = Math.round(price * percentage);   
    }
    
    public void lettercount ()
    {
        if (title == null)
        return;
        
        int lettercount = 0;
        
        for (int i = 0; i < title.length(); i++)
        {
        
            if (Character.isLetter(title.charAt(i)))
                lettercount++;
                
        }
        
        System.out.println("There are " + lettercount + " letters in the title");
    
        
        
       
    }
    
    public void bookcheck()
    {
        if (pricespecial > 0)
        {
        System.out.println("########################");
        System.out.println("# Title: " + title);
        System.out.println("# Author: " +author);
        System.out.println("# Published: " + year);
        System.out.println("# was £ " + price);
        System.out.println("# now £ " + pricespecial);
        System.out.println("########################");
        }
        
        else
        {
        System.out.println("########################");
        System.out.println("# Title: " + title);
        System.out.println("# Author: " +author);
        System.out.println("# Published: " + year);
        System.out.println("# £ " + price);
        System.out.println("########################");   
        }
    }
    
}

Thanks.