java - try catch 异常无限 while 循环

Question

这个问题已经有答案了:

How to handle infinite loop caused by invalid input (InputMismatchException) using Scanner (5 个回答)

已关闭 5 年前。

我希望程序在捕获异常时重新执行 while 循环 - 异常正在接收文本输入。相反，它会使用下面的代码继续执行 while 循环，我希望它再次请求用户输入。

import java.util.InputMismatchException;
import java.util.Scanner;

public class NumberGuess {
    public static void main(String[] args) {

        Scanner Scanner = new Scanner(System.in);

        int between = 100;
        int secretNumber = (int)(Math.random()*between);
        int inputNum = 0;
        int guesses = 0;

        System.out.println("Please enter your guess: ");
        inputNum = Scanner.nextInt();
        guesses++;

        // ####  Loop here ####
        while (inputNum != secretNumber) {  
            // Try catch
            try {

            // number too high or too low
            if (inputNum > 100 | inputNum < 0) {
                System.out.println("Please enter a guess between 0 and " + between + ".");
                inputNum = Scanner.nextInt();
            }

            // less than secretNumber
            if (inputNum < secretNumber) {
                System.out.println("Try higher");
                inputNum = Scanner.nextInt();
                guesses++;
            }

            // greater than secretNumber
            if (inputNum > secretNumber) {
                System.out.println("Try lower");
                inputNum = Scanner.nextInt();
                guesses++;
            }
            }
            catch(InputMismatchException e){
                System.out.println("Invalid Input");
            }
        }


        System.out.println("\nWell done! The secret number was " + secretNumber + "." + "\nYou took " + guesses +  " guesses.");
        }

}

输出:

Invalid Input
Try higher
Invalid Input
Try higher
Invalid Input
Try higher
Invalid Input
Try higher
Invalid Input
Try higher
Invalid Input
Try higher
Invalid Input
Try higher

Answer 1

研究有关扫描仪的文档:

When a scanner throws an InputMismatchException, the scanner will not pass the token that caused the exception, so that it may be retrieved or skipped via some other method.

如果您捕获异常，扫描仪将留在尝试读取号码之前的位置。您必须在 catch block 中使用 nextLine 来推进它。