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Scanner in, 这样的话, in的buffer区域中就没有之前存留的\n, 那么这个时候我们再输入一行, 则不会出现\r被读取的问题.

    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();}
}