Java程序中实现用户输入密码的循环验证与错误处理

import java.util.Scanner;

public class SecurePasswordInput {

    public static void main(String[] args) {
        // 定义密码复杂性常量
        final int MIN_LENGTH = 8;
        final int MIN_UPPERCASE = 1;
        final int MIN_DIGITS = 1;
        final int MIN_SPECIAL = 1;
        final int MAX_RETRIES = 3; // 设置最大重试次数

        Scanner sc = new Scanner(System.in);

        System.out.println("Enter Name: ");
        String name = sc.nextLine();
        int spacePosition = name.indexOf(" "); // 用于生成用户名

        System.out.println("\nEnter Birthday (MM DD YYYY): ");
        String birthday = sc.nextLine();

        String password = ""; // 用于存储最终的有效密码
        boolean isValidPassword = false;
        int retryCount = 0;

        // 密码输入和验证的循环
        while (!isValidPassword && retryCount < MAX_RETRIES) {
            System.out.println("\nEnter password (Attempt " + (retryCount + 1) + "/" + MAX_RETRIES + "): ");
            password = sc.nextLine(); // 获取用户输入的密码

            // 初始化计数器
            int uppercaseCounter = 0;
            int digitCounter = 0;
            int specialCounter = 0;
            int spaceCounter = 0;

            // 遍历密码字符进行验证
            for (int i = 0; i < password.length(); i++) {
                char c = password.charAt(i);
                if (Character.isUpperCase(c)) {
                    uppercaseCounter++;
                } else if (Character.isDigit(c)) {
                    digitCounter++;
                } else if (Character.isWhitespace(c)) { // 检查所有空白字符
                    spaceCounter++;
                } else if ("$#?!_=%.".indexOf(c) != -1) { // 更灵活的特殊字符检查
                    specialCounter++;
                }
            }

            // 检查所有密码复杂性条件
            boolean lengthValid = password.length() >= MIN_LENGTH;
            boolean uppercaseValid = uppercaseCounter >= MIN_UPPERCASE;
            boolean digitValid = digitCounter >= MIN_DIGITS;
            boolean specialValid = specialCounter >= MIN_SPECIAL;
            boolean noSpaces = spaceCounter == 0; // 密码不能包含空格

            // 判断密码是否完全有效
            if (lengthValid && uppercaseValid && digitValid && specialValid && noSpaces) {
                isValidPassword = true; // 密码有效，设置标志退出循环
                System.out.println("Password accepted.");
            } else {
                // 密码无效，打印详细错误信息
                System.out.println("Invalid password. Please review the requirements:");
                if (!lengthValid) System.out.println("- Password must be at least " + MIN_LENGTH + " characters long.");
                if (!noSpaces) System.out.println("- Password cannot contain spaces or other whitespace characters.");
                if (!uppercaseValid) System.out.println("- Password must contain at least " + MIN_UPPERCASE + " uppercase character(s).");
                if (!digitValid) System.out.println("- Password must contain at least " + MIN_DIGITS + " digit(s).");
                if (!specialValid) System.out.println("- Password must contain at least " + MIN_SPECIAL + " special character(s) (e.g., $#?!_=%.).");

                retryCount++; // 增加重试计数
            }
        }

        // 检查是否因为重试次数耗尽而退出循环
        if (!isValidPassword) {
            System.out.println("\nMaximum password retry attempts reached. Program terminating.");
            sc.close(); // 关闭Scanner
            System.exit(1); // 使用非零状态码表示异常退出
        }

        // 如果密码有效，则继续打印登录详情
        System.out.println("\nYour login details:");
        System.out.println("Name    : " + name);
        System.out.println("Birthday: " + birthday);

        // 生成用户名（原始逻辑，可能需要更健壮的错误处理）
        String username;
        if (spacePosition != -1 && name.length() >= spacePosition + 3) {
             username = name.substring(0, 2) + name.substring(spacePosition + 3) + birthday.substring(3, 5);
        } else {
             // 如果姓名过短或无空格，提供一个备用生成方式
             username = name.substring(0, Math.min(name.length(), 2)) + birthday.substring(3, 5);
        }
        System.out.println("Username: " + username);
        System.out.println("Password: " + password);

        sc.close(); // 关闭Scanner
    }
}