关于java中nextline读取空白行的问题

最近在做java作业, 发现了一个问题, 就是nextline其实会接收缓冲区的\r, 使得在程序运行时nextline像是跳过了一样, 其实不然, 它只是读取了上一个enter时的\r, 如我的如下功能代码

    public void run() {
        Scanner scan = new Scanner(System.in);
        int ord, book_order;
        int flag = 0;
        String isbn = new String();
        String nme = new String();
        while (flag == 0) {
            System.out.println("Function List:");
            System.out.println("1.Show the book list");
            System.out.println("2.Find book");
            System.out.println("3.Add book");
            System.out.println("4.Delete book");
            System.out.println("0.Exit");
            System.out.println("Please input the functon order:");
            ord = scan.nextInt();
            switch (ord) {
            case 0: {
                flag = 1;
                break;
            }
            case 1: {
                Print();
                break;
            }
            case 2: {
            	Scanner in = new Scanner(System.in);
                System.out.println("Please input the ISBN of book you want to find:");
                isbn = in.nextLine();
                book_order = Find(isbn);
                if (book_order != 0) {
                    System.out.println("Success!");
                    System.out.println("Name:" + books[book_order].name);
                    System.out.println("ISBN:" + books[book_order].ISBN);
                    System.out.println();
                } else {
                    System.out.println("Error!No such book!");
                    System.out.println();
                }
                break;
            }
            case 3: {
            	Scanner in = new Scanner(System.in);
                System.out.println("Please input the name of the book:");
                nme = scan.nextLine();
                System.out.println("Please input the ISBN of the book:");
                isbn = scan.nextLine();
                if (Add(nme, isbn)) {
                    System.out.println("Add successfully!");
                    System.out.println();
                } else {
                    System.out.println("Failed to add!It's out of range!");
                    System.out.println();
                }
                break;
            }
            case 4: {
                System.out.println("Please input the ISBN of book you want to delete:");
                isbn = scan.nextLine();
                if (Del(isbn)) {
                    System.out.println("Delete successfully!");
                    System.out.println();
                } else {
                    System.out.println("Failed to delete!No such book!");
                    System.out.println();
                }
                break;
            }
            }
        }
        scan.close();
    }
}

在这里, 我一开始就已经实例化了一个scanner对象, 命名为scan, 然后在输入功能选项时我们调用了nextInt, 那么在输入完之后, 整数被读取进去了, 但是那个\r还留在scan的buffer区域, 所以, 如果我们添加书籍的话, 再次使用scan的nextline来读取书名的话, nextline就会得到scan的buffer区域中的\r,导致程序错误, 所以,在这里看到老师的代码之后, 得到启发, 重新新建一个scanner对象, 在这里可以使用in

    public void run() {
        Scanner scan = new Scanner(System.in);
        int ord, book_order;
        int flag = 0;
        String isbn = new String();
        String nme = new String();
        while (flag == 0) {
            System.out.println("Function List:");
            System.out.println("1.Show the book list");
            System.out.println("2.Find book");
            System.out.println("3.Add book");
            System.out.println("4.Delete book");
            System.out.println("0.Exit");
            System.out.println("Please input the functon order:");
            ord = scan.nextInt();
            switch (ord) {
            case 0: {
                flag = 1;
                break;
            }
            case 1: {
                Print();
                break;
            }
            case 2: {
            	Scanner in = new Scanner(System.in);
                System.out.println("Please input the ISBN of book you want to find:");
                isbn = in.nextLine();
                book_order = Find(isbn);
                if (book_order != 0) {
                    System.out.println("Success!");
                    System.out.println("Name:" + books[book_order].name);
                    System.out.println("ISBN:" + books[book_order].ISBN);
                    System.out.println();
                } else {
                    System.out.println("Error!No such book!");
                    System.out.println();
                }
                break;
            }
            case 3: {
            	Scanner in = new Scanner(System.in);
                System.out.println("Please input the name of the book:");
                nme = in.nextLine();
                System.out.println("Please input the ISBN of the book:");
                isbn = in.nextLine();
                if (Add(nme, isbn)) {
                    System.out.println("Add successfully!");
                    System.out.println();
                } else {
                    System.out.println("Failed to add!It's out of range!");
                    System.out.println();
                }
                break;
            }
            case 4: {
                System.out.println("Please input the ISBN of book you want to delete:");
                isbn = scan.nextLine();
                if (Del(isbn)) {
                    System.out.println("Delete successfully!");
                    System.out.println();
                } else {
                    System.out.println("Failed to delete!No such book!");
                    System.out.println();
                }
                break;
            }
            }
        }
        scan.close();
    }
}

运行结果如下:

此外, 也可以和cpp一样, 使用一次scan.nextLine将那个\r读取.