当我键入 2 个单词时，代码不断给出输入不匹配异常

Question

if (userOption == 2) {
    System.out.println("You have chosen produce! Please enter (1) for organic or (0) for non-organic.");
    type = sc.nextInt();
    System.out.println("Please enter a name for this produce.");
    name = sc.next();
    sc.nextLine();
    System.out.println("Please enter the amount of calories.");
    calories = sc.nextInt();
    System.out.println("Please enter the amount of carbohydrates.");
    carbohydrates = sc.nextInt();
    list.add(new Produce(name, calories, carbohydrates, type));
}

您好，当我在单词之间为"名称"输入添加空格时，当我不输入卡路里时，它会InputMismatchError卡路里出错，直到用户输入"名称"，卡路里甚至不应该得到输入。谢谢:)

Answer 1

您的输入是包含空格的"牛肉炸玉米饼"。Java-Doc 指出：

扫描程序使用分隔符模式将其输入分解为标记， 默认情况下与空格匹配。

因此，您的sc.next();返回"牛肉"，将"Taco"留在流中。然后，您的下一个sc.nextInt();返回"Taco"，它不是整数，并导致一个InputMismatchException，其中指出：

输入不匹配异常 - 如果下一个标记与整数正则表达式不匹配，或者超出范围

---

要修复它，请尝试以下操作：

System.out.println("You have chosen produce! Please enter (1) for organic or (0) for non-organic.");
int type = sc.nextInt();
// Clear the input
sc.nextLine();
System.out.println("Please enter a name for this produce.");
// Read in the whole next line (so nothing is left that can cause an exception)
String name = sc.nextLine();

Answer 2

您似乎正在尝试将String输入到Integer中。要捕获这一点，您可以将代码更改为如下所示的内容：

if (userOption == 2) {
            System.out.println("You have chosen produce! Please enter (1) for organic or (0) for non-organic.");
            try {
                type = sc.nextInt();
            } catch (InputMismatchException e) {
                System.out.println("Wrong format entered.");
                // ask question again or move on.
            }
            System.out.println("Please enter a name for this produce.");
            name = sc.next();
            sc.nextLine();
            System.out.println("Please enter the amount of calories.");
            calories = sc.nextInt();
            System.out.println("Please enter the amount of carbohydrates.");
            carbohydrates = sc.nextInt();
        list.add(new Produce(name, calories, carbohydrates, type));
    }

try/catch 将捕获此异常并告诉用户他们做错了什么。