Question

为什么我的代码会给我一个错误？如果用户输入了错误的号码，代码是否应该输入新的有效号码？好像它并没有让我把喜爱改成新的价值。我怎么能解决这个问题？

# The `with` statement is the proper way to open a file.
# It opens the file, and closes it accordingly when you leave it.
with open('foo.txt', 'r') as file:
    # You can directly iterate your lines through the file.
    for line in file:
        # You want a new sum number for each line.
        sum_2 = 0
        # Creating your list of numbers from your string.
        lineNumbers = line.split(' ')
        for number in lineNumbers:
            # Casting EACH number that is still a string to an integer...
            sum_2 += int(number) ** 2
        print 'For this line, the sum of the squares is {}.'.format(sum_2)

控制台输出：

package RobB;

import java.util.Scanner;

public class FavoriteNum {

    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int[] num = new int[10];
        int favorite = 0;

        System.out.print("Enter your favorite number: ");
        try {
            favorite = scan.nextInt();
        }
        catch (Exception e) {
            System.out.println("Enter an integer!");
            System.out.print("Enter your favorite number: ");

            favorite = scan.nextInt();
        }

        for (int i = 0; i < 10; i++) {
            System.out.print("Enter a random number (" + Math.abs(((i + 1) - 10)) + " to go): ");
            num[i] = scan.nextInt();
        }
    }
}

Answer 1

这是一个带有while循环的替代方法：

boolean validInput = false;
while (!validInput) {
   try {
        System.out.print("Enter your favourite number: ");
        favorite = scan.nextInt();
        validInput = true;
    }
    catch (Exception e) {
        System.out.println("Enter an integer!");
    }
}

Answer 2

在catch条款中扫描输入似乎不是最好的主意。我建议使用do-while循环，允许离开此循环的条件可以是boolean标志，当您确认最终输入有效Integer时，该状态将被更改。您可能还需要考虑使用Scanner的{{1}}方法来检查是否提供了正确的输入，如果在您的情况下不是真的需要，则不会抛出任何异常。以下是 ronhash的答案的一些变体，但使用了hasNextInt()循环：

do-while

编辑：我编辑了代码，因为前一个代码不合适而且错误。

Scanner Try Catch语句导致java.util.InputMismatchException

2 个答案: