用户输入的 Java 验证错误

Question

我有以下代码，其中的想法是用户输入两个数字，然后计算两个数字的总和。 如果值无效，例如输入一个字符，应该输出一条错误消息，但我不断收到错误

Java

package calculator;
import java.util.Scanner;

public class calculator {
    /**
     * @param args
     */
    public static void main(String[] args) {
        double n1, n2;
        String operation;
        Scanner scannerObject = new Scanner(System.in);

        System.out.println("Enter first number");
        n1 = scannerObject. nextDouble();


        System.out.println("Enter second number");
        n2 = scannerObject. nextDouble();

        Scanner op = new Scanner(System.in);
        System.out.println("Enter your operation");
        operation = op.next();

        switch (operation)  {
        case "+":
            System.out.println("Your answer is " + (n1 + n2));
            break;

        case "-":
            System.out.println("Your answer is " + (n1 - n2));
            break;

        case "/":
            System.out.println("Your answer is " + (n1 / n2));
            break;

        case "*":
            System.out.println("Your asnwer is " + (n1 * n2));
            break;

        default:
            System.out.println("I do not know!");}
        }
            int function(){
                Scanner input = new Scanner(System.in);   
                System.out.print("Enter an integer between 1-100: ");   
                int range;
            while(true){   
                    if(input.hasNextInt()){   
                    range = input.nextInt();
                    if(0<=range && range <= 100)
                        break;
                    else
                        continue;
                    }
                    input.nextLine();  //Comsume the garbage value
                    System.out.println("Enter an integer between 1-100:");
                }
                return range;
                }

             }

这些是我收到的错误消息:

错误

Exception in thread "main" java.util.InputMismatchException
    at java.util.Scanner.throwFor(Scanner.java:909)
    at java.util.Scanner.next(Scanner.java:1530)
    at java.util.Scanner.nextDouble(Scanner.java:2456)
    at calculator.calculator.main(calculator.java:14)

我尝试了很多不同的方法，但无法让它按照我想要的方式工作。

有人可以帮忙吗？

感谢您的阅读

Answer 1

此异常由 Scanner 类的实例引发，以指示检索到的 token 与预期类型的​​模式不匹配，或者检索到的 token 超出范围。

您可以在此处查看异常的文档:https://docs.oracle.com/javase/7/docs/api/java/util/InputMismatchException.html

取自 Scanner 上的文档

double nextDouble()

Returns the next token as a long. If the next token is not a float or is out of range, InputMismatchException is thrown.

我怀疑您输入的电话号码不正确。确保您的输入格式正确。

您还应该设置扫描仪的区域设置，因为某些区域设置需要逗号,而不是点。，如:

Scanner scanner = new Scanner(System.in).useLocale(Locale.US);