Java密码验证与程序流程控制：实现用户输入校验与重试机制

import java.util.Scanner;

public class PasswordValidator {

    // 定义密码验证常量
    private static final int MAX_PASSWORD_LENGTH = 8;
    private static final int MIN_UPPERCASE = 1;
    private static final int MIN_DIGITS = 1;
    private static final int MIN_SPECIAL_CHARS = 1;
    private static final int MAX_ATTEMPTS = 3; // 最大尝试次数

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in); // 使用单个Scanner实例

        // 获取用户基本信息
        System.out.println("请输入姓名: ");
        String name = scanner.nextLine();
        int spacePosition = name.indexOf(" ");

        System.out.println("\n请输入生日 (MM DD YYYY): ");
        String birthday = scanner.nextLine();

        String password = "";
        boolean isValidPassword = false;
        int attempts = 0;

        // 密码输入与验证循环
        while (!isValidPassword && attempts < MAX_ATTEMPTS) {
            System.out.println("\n请输入密码 (尝试 " + (attempts + 1) + "/" + MAX_ATTEMPTS + "): ");
            password = scanner.nextLine();

            // 重置计数器，为当前尝试做准备
            int uppercaseCounter = 0;
            int digitCounter = 0;
            int specialCounter = 0;
            int spaceCounter = 0;

            // 遍历密码字符进行类型判断
            for (char c : password.toCharArray()) {
                if (Character.isUpperCase(c)) {
                    uppercaseCounter++;
                }
                if (Character.isDigit(c)) {
                    digitCounter++;
                }
                // 检查是否为预定义的特殊字符
                if (c == '$' || c == '#' || c == '?' || c == '!' || c == '_' || c == '=' || c == '%' || c == '.') {
                    specialCounter++;
                }
                if (Character.isWhitespace(c)) { // 使用Character.isWhitespace更全面地检查空格
                    spaceCounter++;
                }
            }

            // --- 密码验证逻辑判断 ---
            boolean lengthValid = password.length() >= MAX_PASSWORD_LENGTH;
            boolean uppercaseValid = uppercaseCounter >= MIN_UPPERCASE;
            boolean digitValid = digitCounter >= MIN_DIGITS;
            boolean specialCharValid = specialCounter >= MIN_SPECIAL_CHARS;
            boolean noSpaces = spaceCounter == 0; // 密码不允许包含空格

            // 综合判断密码是否有效
            if (lengthValid && uppercaseValid && digitValid && specialCharValid && noSpaces) {
                isValidPassword = true;
                System.out.println("密码符合要求，已接受。");
            } else {
                // 密码无效，输出具体错误信息
                System.out.println("密码无效，请检查以下要求：");
                if (!lengthValid) {
                    System.out.println("- 密码长度至少为 " + MAX_PASSWORD_LENGTH + " 个字符。");
                }
                if (!uppercaseValid) {
                    System.out.println("- 密码至少包含 " + MIN_UPPERCASE + " 个大写字母。");
                }
                if (!digitValid) {
                    System.out.println("- 密码至少包含 " + MIN_DIGITS + " 个数字。");
                }
                if (!specialCharValid) {
                    System.out.println("- 密码至少包含 " + MIN_SPECIAL_CHARS + " 个特殊字符 ($, #, ?, !, _, =, %, .)。");
                }
                if (!noSpaces) {
                    System.out.println("- 密码不能包含空格。");
                }
                attempts++; // 尝试次数加一
            }
        }

        scanner.close(); // 关闭Scanner，释放资源

        // 根据最终验证结果决定程序流程
        if (isValidPassword) {
            // 密码有效，打印用户登录信息
            System.out.println("\n--- 您的登录详情 ---");
            System.out.println("姓名    : " + name);
            System.out.println("生日    : " + birthday);

            // 生成用户名，注意此处逻辑可能因姓名格式而异，需要更健壮的错误处理
            String username = "";
            if (spacePosition != -1 && name.length() > 2 && name.length() > spacePosition + 3) {
                username = name.substring(0, 2) + name.substring(spacePosition + 3) + birthday.substring(3, 5);
            } else {
                // 姓名过短或无空格时的备用逻辑
                username = name.substring(0, Math.min(name.length(), 2)) + birthday.substring(3, 5);
            }
            System.out.println("用户名  : " + username);
            System.out.println("密码    : " + password); // 实际应用中不应直接打印密码
        } else {
            // 达到最大尝试次数，密码仍无效，终止程序
            System.out.println("\n已达到最大密码尝试次数。程序终止。");
            System.exit(1); // 使用非零状态码表示异常退出
        }
    }
}

// 示例：将验证逻辑封装到方法中
public static boolean isValidPassword(String password) {
    int uppercaseCounter = 0;
    int digitCounter = 0;
    int specialCounter = 0;
    int spaceCounter = 0;

    for (char c : password.toCharArray()) {
        if (Character.isUpperCase(c)) {
            uppercaseCounter++;
        }
        if (Character.isDigit(c)) {
            digitCounter++;
        }
        if (c == '$' || c == '#' || c == '?' || c == '!' || c == '_' || c == '=' || c == '%' || c == '.') {
            specialCounter++;
        }
        if (Character.isWhitespace(c)) {
            spaceCounter++;
        }
    }

    boolean lengthValid = password.length() >= MAX_PASSWORD_LENGTH;
    boolean uppercaseValid = uppercaseCounter >= MIN_UPPERCASE;
    boolean digitValid = digitCounter >= MIN_DIGITS;
    boolean specialCharValid = specialCounter >= MIN_SPECIAL_CHARS;
    boolean noSpaces = spaceCounter == 0;

    return lengthValid && uppercaseValid && digitValid && specialCharValid && noSpaces;
}

// 在主方法中调用：
// if (isValidPassword(password)) { ... }