登录注册-----java案例

import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;
public class Login {
    private Map<String, String> users;
    public Login() {
        users = new HashMap<>();
    }
    public void register(String username, String password) {
        if (!users.containsKey(username)) {
            users.put(username, password);
            System.out.println("注册成功！");
        } else {
            System.out.println("该用户名已被注册，请尝试其他用户名！");
        }
    }
    public boolean login(String username, String password) {
        if (users.containsKey(username) && users.get(username).equals(password)) {
            System.out.println("登录成功！");
            return true;
        } else {
            System.out.println("用户名或密码错误，请重新登录！");
            return false;
        }
    }
    public static void main(String[] args) {
        Login system = new Login();
        Scanner scanner = new Scanner(System.in);
        boolean isLoggedIn = false;
        while (!isLoggedIn) {
            System.out.println("请选择操作：");
            System.out.println("1. 注册");
            System.out.println("2. 登录");
            System.out.println("3. 退出");
            int choice = scanner.nextInt();
            switch (choice) {
                case 1:
                    System.out.println("请输入用户名：");
                    String registerUsername = scanner.next();
                    System.out.println("请输入密码：");
                    String registerPassword = scanner.next();
                    system.register(registerUsername, registerPassword);
                    break;
                case 2:
                    System.out.println("请输入用户名：");
                    String loginUsername = scanner.next();
                    System.out.println("请输入密码：");
                    String loginPassword = scanner.next();
                    isLoggedIn = system.login(loginUsername, loginPassword);
                    break;
                case 3:
                    System.out.println("已退出系统！");
                    isLoggedIn = true;
                    break;
                default:
                    System.out.println("无效的选择，请重新输入！");
                    break;
            }
        }
        scanner.close();
    }
}