gistfile1.java

public void BookController {
    
    private static BookController instance = null;
    private BookRepository bookRepository = new PersistentBookRepository();
    
    protected BookController() {}

    public static BookController getInstance() {
        if(instance == null) {
            instance = new BookController();
        }
        return instance;
    }
  
    public List<BookPreview> getAllBookPreviews() {
    
        List<Book> allBooks = bookRepository.getAllBooks();
        List<BookPreview> bookPreviews = new LinkedList<BookPreview>();
    
        for (Book currentBook : allBooks) {
            bookPreviews.add(getBookPreview(currentBook));
        }
    
        return bookPreviews;
    }
  
    public BookPreview getBookPreview(Book book) {
        return new BookPreview(book.getCover, book.getPrologue, book.getChapterByNumber(1));
    }
}