Searching Array Of Objects In Java

'm working on a program that is to act as an inventory for a book store. There are two classes (Store and Book), and numerous methods which you will see in my code. The program is supposed to read in an inventory from a file which contains 10 books (each row in the file represents a book with an ISBN number, the price of the book, and the number in stock)and store this file into an array of type Book[]. There is then to be another method to process a purchase interactively. The Store class is also to keep a count of how many books were sold at the time of closing and also how much was made that day.

I'm having some difficulty figuring out how I should set up the purchase processing method though. I've written out how I think it would be set up (not too familiar with the terminology, but I think it would be called pseudo code?) I'll include that now along with a few other notes.

public Book[] purchase(String isbn, double price, int copies) {
int itemsSold;
double totalMade;
Scanner input = new Scanner(System.in);
System.out.println("Please enter the ISBN number of the book you would like to purchase: ");

[Code] ....

So basically here's what needs to be accomplished with this portion of code:

1.Ask the user to enter the ISBN number of the book they'd like to purchase.
2.Search the array for the object that contains that ISBN.
3.If the ISBN isn't found in the array, display a message stating that we don't have that book.
4.If the ISBN is found but the number of copies is 0, display a message saying the book is out of stock.
5.If the ISBN is found and the number of copies is greater than 0, ask the user how many copies they'd like to purchase.
6.If the number they enter is greater than the number of copies of that book in the array, display a message stating that and ask them to enter another quantity.
7.Once the purchase is complete I need to update the array by subtracting the number of copies of that particular book that was purchased.
8.Print the updated array.
9.Display a count of how many books were purchased, and how much money was made from the purchase.

I know that code has a lot of holes in it, but I'm just trying to get everything together and figure out how to do each step.

The part I'm stuck on right now is trying to figure out how to search the array to first see if the ISBN that was entered is in the array, and then to find the number of copies of the book with that ISBN number.

In case it will visualize what this array looks like, here's a print out of the array from a sample run I just did.

ISBN: 1234567, Price: 31.670000, Copies: 0
ISBN: 1234444, Price: 98.500000, Copies: 4
ISBN: 1235555, Price: 27.890000, Copies: 2
ISBN: 1235566, Price: 102.390000, Copies: 6

[Code] ....