ATM机 循环

import java.util.Scanner;

public class ATM {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);

        String username = "zhangsan";
        String password = "123";
        double money = 500;
        
        System.out.println("请输入账号：");
        String iptId = scan.next();
        System.out.println("请输入密码：");
        String iptPwd = scan.next();

        boolean loginState = false;

        if (iptId.equals(username) && iptPwd.equals(password)) {
            System.out.println("欢迎，成功");
            loginState = true;
        } else {
            System.out.println("错了！");
        }

        if (loginState) {
            System.out.println("1. 存 2. 取 3. 查 4. 退:");
            int opt = scan.nextInt();
            switch (opt) {
                case 1:
                    System.out.println("请输入存款金额:");
                    double account = scan.nextDouble(); // 100
                    money += account; // money= money+account
                    System.out.println("卡上余额：" + money);
                    break;
                case 2:
                    System.out.println("请输入取款金额：");
                    double m = scan.nextDouble();
                    if (m > money) {
                        System.out.println("卡上余额不足");
                    } else {
                        money -= m;
                        System.out.println("卡上余额：" + money);
                    }
                    break;
                case 3:
                    System.out.println("卡上余额：" + money);
                    break;
                case 4:
                    System.out.println(886);
                    break;
            }
        }


    }
}