Question

我正在尝试使用java中的do-while循环创建一个简单的菜单。我的代码如下所示：

int choice;
    Scanner scanChoice = new Scanner(System.in);
    do {
        System.out.println("Pick an option. 1 2 or 3.");
        System.out.println("1. Apple");
        System.out.println("2. Pear");
        System.out.println("3. Pineapple");

        choice = scanChoice.nextInt();
    } while (choice < 1 || choice > 3);

    System.out.println("You picked " + choice);

问题是，每次我尝试运行它时，都会抛出“java.util.NoSuchElementException”。完整错误如下：

Exception in thread "main" java.util.NoSuchElementException
at java.util.Scanner.throwFor(Scanner.java:862)
at java.util.Scanner.next(Scanner.java:1485)
at java.util.Scanner.nextInt(Scanner.java:2117)
at java.util.Scanner.nextInt(Scanner.java:2076)
at mainPackage.Main.fruitMenu(Main.java:135)
at mainPackage.Main.main(Main.java:103)

我知道这是因为scanChoice.hasNextInt()返回false，但我不知道如何解决这个问题。当我添加if语句（if (scanChoice.hasNextInt())）时，方法scanChoice.hasNextInt()仍然返回false，因此它只是通过初始化变量choice的行，并且该变量永远不会被初始化。 / p>

任何人都知道如何解决这个问题？

编辑：问题是它不会等待用户输入另一个整数。函数scanchoice.nextInt()和函数scanChoice.nextLine()都不会立即返回任何值，而无需等待用户输入值。有什么方法让它等待输入？

Answer 1

它似乎一直对我有用。对于任何有效的整数，它按预期工作，要么接受输入要么通过循环，当输入无效输入如“abcd”时它会抛出InputMismatchException，这无论如何都是预期的行为。

Online Java compiler IDE

Answer 2

我让您的代码更加强大。它捕获字母数字字符并再次显示菜单，而不是使用InputMismatchException异常终止。

这是一次试运行。

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这是代码。我打电话给Scanner nextLine方法。

Pick an option. 1 2 or 3.
1. Apple
2. Pear
3. Pineapple
x
Pick an option. 1 2 or 3.
1. Apple
2. Pear
3. Pineapple
asdf
Pick an option. 1 2 or 3.
1. Apple
2. Pear
3. Pineapple
2
You picked 2

在java中使用Do-while循环的简单菜单

2 个答案: