验证一个整数并使其成为5位数 [英] validate an integer AND make it 5 digits

问题描述

我正在学习我的第一个java课程。我需要要一个邮政编码。我知道如果他们不输入5位数，如何要求新输入，但如果输入非整数，我如何要求新输入？

I'm taking my very first java class. I need to ask for a zip code. I know how to ask for new input if they don't enter 5 digits, but how do I also ask for new input if they enter a non-integer?

这里就是我拥有的：

import java.util.Scanner;

public class AndrewDemographics {

    public static void main(String[] args) {
        Scanner stdIn = new Scanner(System.in);
        int zip;                // 5 digit zip

        System.out.print("Enter your 5 digit zip code: ");
        zip = stdIn.nextInt();
        while ((zip < 10000) || (zip > 99999))  {
            // error message
            System.out.println("Invalid Zip Code format.");
            System.out.println("");
            System.out.println("Enter your 5 digit zip code: ");
            zip = stdIn.nextInt();
        } //end if zip code is valid
    }
}

推荐答案

要支持以 0 开头的邮政编码，您需要将邮政编码存储在字符串中，然后最简单的验证它使用正则表达式：

To support zip codes starting with 0, you need to store the zip code in a String, and then it's easiest to validate it using a regex:

Scanner stdIn = new Scanner(System.in);
String zip;
do {
    System.out.print("Enter your 5 digit zip code: ");
    zip = stdIn.next();
} while (! zip.matches("[0-9]{5}"));

如果要打印错误信息，可以这样做，使用 nextLine（）所以只需按Enter键也会打印错误信息：

If you want to print error message, you can do it like this, which uses nextLine() so simply pressing enter will print error message too:

Scanner stdIn = new Scanner(System.in);
String zip;
for (;;) {
    System.out.print("Enter your 5 digit zip code: ");
    zip = stdIn.nextLine().trim();
    if (zip.matches("[0-9]{5}"))
        break;
    System.out.println("Invalid Zip Code format.");
    System.out.println();
}

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