尝试捕获异常无限循环[重复]

Question

这个问题在这里已有答案：

• How to handle infinite loop caused by invalid input (InputMismatchException) using Scanner 5个答案

我希望程序在捕获异常时重新执行while循环 - 接收文本输入的异常。相反，它继续使用下面的代码循环，我希望它再次要求用户输入。

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Scanner上的文档：

当扫描程序抛出InputMismatchException时，扫描程序将不会传递导致异常的令牌，因此可以通过其他方法检索或跳过它。

如果您发现异常，则在尝试读取数字之前，扫描仪将保留原样。你必须在追踪区内用nextLine推进它。

Answer 2

|是合乎逻辑的运营商。使用条件||

 if (inputNum > 100 || inputNum < 0) {

Answer 3

进行2次更改，如下所示可以帮助您实现所需的功能。

1将if (inputNum > 100 | inputNum < 0) {更改为if (inputNum > 100 || inputNum < 0) {

如果输入非数字数字（例如a），则可以捕获InputMismatchException异常。

1. 当InputMismatchException发生异常时，添加代码调用Scanner.next()以便可以在Console中重新输入数字。

更改

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

        }

至

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

        }

通过以上更改，测试如下：

Please enter your guess: 
60
Try higher
80
Try higher
90
Try lower
a
Invalid Input
Try lower
80
Try higher
85
Try lower
84
Try lower
83
Try lower
82
Try lower
81

Well done! The secret number was 81.
You took 9 guesses.