java - 如何验证读取 1,000 到 999,999 范围内的数字输入的代码？

Question

我让它取一个 1000 到 999999 范围内的数字，还允许使用逗号。我现在需要验证代码并提供适当的错误消息。

import java.util.Scanner;

public class ConsoleReader {

public static void main(String[] args) {
    // TODO Auto-generated method stub

    // get a connection to the keyboard 
    Scanner in = new Scanner(System.in); 

    // ask the user for input 
    System.out.print("Please enter an integer between 1,000 and 999,999: ");
    // read user's input 
    String number = in.next(); 

    // get the first part (no comma or thousands) 
    String firstPart = number.substring(0, number.length() - 4); 
    // get last three digits 
    String lastThreeDigits = number.substring(number.length() - 3); 

    // print the two without the comma 
    System.out.println(firstPart + lastThreeDigits);
}   
{
if (in.hasNextInt())
{
    String number = in.next();
}
else
{
    System.out.println("Please try again.");
}
}
}

Answer 1

另一种方法是使用正则表达式验证其格式是否有效，替换逗号，将其解析为 int 并确保其在可接受的范围内。

String number = in.next(); 
if (number.matches("\\d{0,2}\\d\\,?\\d{3}") {
    int intNumber = Integer.parseInt(number.replace(",", "");
    if (number >= 1000 && number <= 999999) {
        ...
    }
}