public void addBook(String title, String year, String author) {
        uniqueID++;
        for (Book book : bookMap.values()) {
            if (book.getTitle().equals(title) && (book.getYear().equals(year)) && (book.getAuthor().equals(author))) {
                numberOfCopies++;
            } else {
                Book newBook = new Book(title, year, author, uniqueID, numberOfCopies);
                bookMap.put(uniqueID, newBook);
                numberOfCopies = 1;
            }
        }
    }