java - 如何向数组添加新条目？

Question

对于这个项目，我只能从书堆中删除最上面的一本书，而无法从另一本书下面删除一本书。同样，我不能将一本书添加到另一本书下面。我只需将另一本书放在书堆的顶部即可将其添加到书堆中。在我的代码中，我从书堆中删除了 Book E，但现在我想添加另一本书。如何添加新书(书:F)到myBooks并打印列表？有一个指向我当前输出的屏幕截图的链接。

screenshot of current output

public class Driver
{
    public static void main(String[] args)
    {
        Book[] myBooks = { new Book("A"), new Book("B"), new Book("C"), new Book("D"), new Book("E")};
        PileOfBooksInterface<Book> bookPiles = new PileOfBooks<>();
        System.out.println("Are there any books in the pile? " + bookPiles.isEmpty());

        for (int index = 0; index < myBooks.length; index++)
        {
            Book nextItem = myBooks[index];
            bookPiles.add(nextItem);
        } // end for

        System.out.println("\nTotal books in the pile:");

        for (int index = 0; index < myBooks.length; index++) 
        {
            System.out.println(myBooks[index]);
        } // end for

        System.out.println("\nRemoving the last book:");
        bookPiles.remove();
        Object[] arr = (bookPiles.toArray());

        for (int index = 0; index < arr.length; index++) 
        {
            System.out.println(arr[index]);
        } // end for

        System.out.println("\nAdding new book on top of the pile:");
         // ???

    }
}

Answer 1

有了书堆，你不再需要一堆书本类(class)，并且会按照你期望的方式工作。

public class Driver {
    public static void main(String[] args) {
        Stack<Book> bookPiles = Arrays.asList(new Book("A"), new Book("B"), new Book("C"), new Book("D"), new Book("E")).stream()
            .collect(Collectors.toCollection(Stack::new));
        System.out.println("Are there any books in the pile? " + !bookPiles.isEmpty());
        System.out.println("\nTotal books in the pile:");
        bookPiles.stream().forEach(System.out::println);
        System.out.println("\nRemoving the last book:");
        bookPiles.pop();
        bookPiles.stream().forEach(System.out::println);
        System.out.println("\nAdding new book on top of the pile:");
        bookPiles.push(new Book("F"));
        bookPiles.stream().forEach(System.out::println);
    }
}

如果 PileOfBooks 已经编写并且已知可以按照您所描述的方式工作，那么您只需将一本书添加到 PileOfBooks 中，就像开始添加书籍时所做的那样。

bookPiles.add(new Book("F"));