private void addBook(String isbn, String title, String synopsis, int quantity) {
        Book book = new Book();
        book.setIsbn(isbn);
        book.setTitle(title);
        book.setSynopsis(synopsis);
        isbns_to_books.put(isbn, book);
        isbns_to_quantities.put(isbn, quantity);
    }
private void addBook ( String isbn , String title , String synopsis , int quantity ) { Book book = new Book ( ) ; book . setIsbn ( isbn ) ; book . setTitle ( title ) ; book . setSynopsis ( synopsis ) ; isbns_to_books . put ( isbn , book ) ; isbns_to_quantities . put ( isbn , quantity ) ; }
Adds the book.

@param isbn the isbn
@param title the title
@param synopsis the synopsis
@param quantity the quantity