Java基础学习：SIN号识别程序0开头9位输入报错问题求助

修复说明 #

• 输入处理改为字符串类型，避免int自动截断前导0的问题，同时直接通过字符串长度判断是否为9位，逻辑更简单
• 修正0和8开头的判断条件，把永远无法成立的逻辑与&&改为逻辑或||
• 直接取字符串第一位判断所属地区，不需要循环取最高位，简化逻辑

修复后完整代码 #

import java.util.Scanner;

public class FirstDigitSIN {
    public static void main(String[] args) {
        Scanner kb = new Scanner(System.in);
        System.out.print("Enter a SIN number :");
        String input = kb.nextLine().trim();
        
        // 校验是否为纯数字
        boolean isNumber = true;
        for (char c : input.toCharArray()) {
            if (!Character.isDigit(c)) {
                isNumber = false;
                break;
            }
        }
        
        if (!isNumber) {
            System.out.println("Error message goes here. Here you can tell them that you want them to enter an integer and not a string.");
        } else if (input.length() != 9) {
            System.out.println("Invalid Entry");
        } else {
            char firstDigit = input.charAt(0);
            switch (firstDigit) {
                case '1':
                    System.out.println(" Registered in Atlantic Canada ");
                    break;
                case '2':
                case '3':
                    System.out.println(" Registered in Quebec ");
                    break;
                case '4':
                case '5':
                    System.out.println(" Registered in Ontario ");
                    break;
                case '6':
                    System.out.println(" Registered in Prairie Provinces, NWT, Nunavut, Northwest Ontario ");
                    break;
                case '7':
                    System.out.println(" Registered in Pacific region ");
                    break;
                case '9':
                    System.out.println(" A temporary SIN ");
                    break;
                case '0':
                case '8':
                    System.out.println("Not used");
                    break;
            }
        }
        System.out.println(" *** End of program *** ");
    }
}

内容的提问来源于stack exchange，提问作者Divya Patel