我可以使用NumberNumberFormateXeption。即使用户输入字符串或非数字，该程序也应继续

Question

猜数字

import java.util.*;

public class LabExer5A
{
    public static void main(String args[])
    {       
        Scanner Input = new Scanner (System.in); 
        System.out.println("Guess a number between 1 and 50");
        int JPS_Guess = Input.nextInt();
        int JPS_CorrectNum = 25;
        int JPS_NextGuess;  
    do
    {
    try
    {
            if (JPS_Guess == JPS_CorrectNum)
            {
                System.out.println("You got it in ");
            }
            else if (JPS_Guess < JPS_CorrectNum && JPS_Guess >= 1)
            {
                System.out.println("Too low. Try again.");
                JPS_NextGuess = Input.nextInt();
                JPS_Guess = JPS_NextGuess;
            }
            else if (JPS_Guess > JPS_CorrectNum && JPS_Guess <= 50)
            {
                System.out.println("Too High. Try again.");
                JPS_NextGuess = Input.nextInt();
                JPS_Guess = JPS_NextGuess;
            }
            else if(JPS_Guess < 1 || JPS_Guess > 50)
            {
                throw new InputMismatchException();
            }
    }
         catch(InputMismatchException e) 
         {
            System.out.println("Invalid value. Please enter a number between 1 and 50: ");
            JPS_NextGuess = Input.nextInt();
            JPS_Guess = JPS_NextGuess;
         }   
          catch (NumberFormatException ex) 
         {
            System.out.println("Error - Enter Numerical Values Only");
            JPS_NextGuess = Input.nextInt();
            JPS_Guess = JPS_NextGuess;
         }  
    }
    while (JPS_Guess != JPS_CorrectNum);//will rerun the program until the user guess the correct number   
}
}

}

}

我不知道我在哪里犯了错误。要么是使用了 throw catch，要么是因为我重新运行程序的方式。我对使用异常和 try-catch 还很陌生，请帮助并友善。谢谢。

Answer 1

nextInt（）实际上输入其他数据类型时抛出InputMismatchException在非整数输入中，

另一件事是input.nextint（）应始终在try/catch中。在您的代码中，第一个输入和输入任何错误的值之后，将不会捕获例外。

 catch(InputMismatchException e) 
         {
            System.out.println("Invalid value. Please enter a number between 1 and 50: ");
            JPS_NextGuess = Input.nextInt();
            JPS_Guess = JPS_NextGuess;
         }   

我修改了您的代码更简单。我建议您使用布尔值来跟踪是否猜到了这个数字，因此您不必互换猜测。此外，良好的凹痕格式有助于阅读。

import java.util.*;

public class LabExer5A
{
    public static void main(String args[])
    { 
        Scanner Input = new Scanner (System.in); 
        System.out.println("Guess a number between 1 and 50");
        int JPS_CorrectNum=25;
        boolean isGuessed=false;  
        do
        {
            try
            {
                int JPS_Guess = Input.nextInt();
                if (JPS_Guess == JPS_CorrectNum)
                {
                    System.out.println("You got it in ");
                    isGuessed=true;
                }
                else if (JPS_Guess < JPS_CorrectNum && JPS_Guess >= 1)
                {
                    System.out.println("Too low. Try again.");
                }
                else if (JPS_Guess > JPS_CorrectNum && JPS_Guess <= 50)
                {
                    System.out.println("Too High. Try again.");
                }
                else if(JPS_Guess < 1 || JPS_Guess > 50)
                {
                    throw new InputMismatchException();
                }
            }
            catch(InputMismatchException e) 
            {
                System.out.println("Invalid value. Please enter a number between 1 and 50: ");
                Input.next();
            }   
        }
        while (!isGuessed);//will rerun the program until the user guess the correct number   
    }
}