自学Java做的第一个入门项目：ATM银行系统

import java.util.ArrayList;
import java.util.Random;
import java.util.Scanner;

public class ATMSystem {
    public static void main(String[] args) {
        ArrayList<Account> accounts = new ArrayList<>();
        while (true) {
            System.out.println("----------欢迎使用ATM系统----------");
            System.out.println("1.登录账号");
            System.out.println("2.注册账号");
            System.out.println("请选择你要进行的操作:");
            Scanner sc = new Scanner(System.in);
            int command = sc.nextInt();
            switch (command) {
                case 1:
                    login(accounts, sc);
                    break;
                case 2:
                    register(accounts, sc);
                    break;
                default:
                    System.out.println("命令错误！");
            }
        }
    }

    /**
     * 注册账户
     *
     * @param accounts 存储账户对象的集合
     * @param sc       扫描器
     * @return
     */
    private static void register(ArrayList<Account> accounts, Scanner sc) {
        System.out.println("==========欢迎进入到注册操作==========");
        //1.创建一个账户对象，用于后期封装账户信息
        Account account = new Account();

        //2.为这个账户对象录入信息
        System.out.println("请输入账号名称：");
        String name = sc.next();
        account.setName(name);

        while (true) {
            System.out.println("请输入账户密码:");
            String password = sc.next();
            System.out.println("请输入确认密码:");
            String password2 = sc.next();
            if (password.equals(password2)) {
                account.setPassword(password);
                break;
            } else {
                System.out.println("两次输入密码不一致！");
            }
        }

        System.out.println("请设置单次取现额度:");
        double restrictMoney = sc.nextDouble();
        account.setRestrictMoney(restrictMoney);

        String id = getRandomId(accounts);
        account.setId(id);
        System.out.println("恭喜您，" + name + ",您的账户注册成功，您的卡号是：" + id);
        accounts.add(account);
    }

    /**
     * 为账户生成8位与其他账户不同的卡号
     *
     * @return
     */
    private static String getRandomId(ArrayList<Account> accounts) {
        Random r = new Random();
        while (true) {
            //1.生成8位数字
            String id = "";
            for (int i = 0; i < 8; i++) {
                id += r.nextInt(10);
            }

            //2.判断该卡号是否与其他账户卡号重复
            Account account = getAccountById(accounts, id);
            if (account == null) {
                return id;
            }
        }
    }

    /**
     * 根据卡号查询账户对象
     *
     * @param accounts
     * @param id
     * @return
     */
    private static Account getAccountById(ArrayList<Account> accounts, String id) {
        for (int i = 0; i < accounts.size(); i++) {
            Account account = accounts.get(i);
            if (account.getId().equals(id)) {
                return account;
            }
        }
        return null;
    }

    /**
     * 登录账户
     *
     * @param accounts 存储账户对象的集合
     * @param sc       扫描器
     * @return
     */
    private static void login(ArrayList<Account> accounts, Scanner sc) {
        System.out.println("==========欢迎进入到登陆操作==========");
        //1.判断当前系统中有无账号存在
        if (accounts.size() == 0) {
            System.out.println("当前系统无任何账户，请注册后登录！");
            return;
        }

        //2.登陆账号
        while (true) {
            System.out.println("请输入登录的卡号：");
            String id = sc.next();
            Account account = getAccountById(accounts, id);
            if (account != null) {
                while (true) {
                    System.out.println("请输入登陆密码：");
                    String password = sc.next();
                    if (password.equals(account.getPassword())) {
                        System.out.println("登陆成功！欢迎你：" + account.getName() + "，进入操作系统，请开始办理你的业务：");
                        showUserCommand(accounts, sc, account);
                        return;
                    } else {
                        System.out.println("密码错误！请重新输入！");
                    }
                }
            } else {
                System.out.println("卡号不存在！请确认后重新输入！");
            }
        }
    }

    /**
     * 登录操作
     *
     * @param accounts
     * @param sc
     * @param account
     */
    private static void showUserCommand(ArrayList<Account> accounts, Scanner sc, Account account) {
        while (true) {
            System.out.println("==========欢迎进入操作界面==========");
            System.out.println("1.查询");
            System.out.println("2.存款");
            System.out.println("3.取款");
            System.out.println("4.转账");
            System.out.println("5.修改密码");
            System.out.println("6.退出");
            System.out.println("7.注销账号");
            System.out.println("请选择你要进行的操作：");
            int command = sc.nextInt();
            switch (command) {
                case 1:
                    inquire(account);
                    break;
                case 2:
                    deposit(account, sc);
                    break;
                case 3:
                    withdrawals(account, sc);
                    break;
                case 4:
                    transfer(accounts, account, sc);
                    break;
                case 5:
                    changePassword(account, sc);
                    return;
                case 6:
                    return;
                case 7:
                    logout(accounts, account, sc);
                    return;
                default:
                    System.out.println("命令不存在！");
            }
        }
    }

    /**
     * 查询账户对象信息
     *
     * @param account
     */
    private static void inquire(Account account) {
        System.out.println("==========您当前账户详情信息如下==========");
        System.out.println("卡号：" + account.getId());
        System.out.println("户主：" + account.getName());
        System.out.println("余额：" + account.getMoney());
        System.out.println("当前取现额度：" + account.getRestrictMoney());
    }

    /**
     * 向账户内存款
     *
     * @param account
     * @param sc
     */
    private static void deposit(Account account, Scanner sc) {
        System.out.println("==========欢迎进入存款操作==========");
        System.out.println("请输入存款金额：");
        double money = sc.nextDouble();
        account.setMoney(money + account.getMoney());
        System.out.println("存款成功！");
        inquire(account);
    }

    /**
     * 从账户内取款
     *
     * @param account
     * @param sc
     */
    private static void withdrawals(Account account, Scanner sc) {
        System.out.println("==========欢迎进入账户取款操作==========");

        while (true) {
            System.out.println("请输入取钱的金额：");
            double withdrawalsMoney = sc.nextDouble();
            if (withdrawalsMoney > account.getRestrictMoney()) {
                System.out.println("超出每次取款限额！");
            } else {
                if (withdrawalsMoney > account.getMoney()) {
                    System.out.println("您的余额不足！");
                } else {
                    account.setMoney(account.getMoney() - withdrawalsMoney);
                    System.out.println("取款成功！请及时取走您的钱！您当前余额为：" + account.getMoney());
                    return;
                }
            }
        }

    }

    /**
     * 转账
     *
     * @param accounts
     * @param account
     * @param sc
     */
    private static void transfer(ArrayList<Account> accounts, Account account, Scanner sc) {
        System.out.println("==========欢迎进入到转账系统==========");
        if (accounts.size() == 1) {
            System.out.println("该系统中没有其他用户，请注册后再进行转账！");
            return;
        }
        while (true) {
            System.out.println("请输入你要转账的卡号：");
            String id = sc.next();
            //1.判断一：被转账卡号是否为该用户卡号
            if (id.equals(account.getId())) {
                System.out.println("不能给自己转账！");
                continue;
            }
            Account account1 = getAccountById(accounts, id);
            //2.判断二：转账卡号是否存在
            if (account1 != null) {
                String name1 = account1.getName();
                String tip = "*" + name1.substring(1);
                System.out.println("请您输入" + tip + "的姓氏来确认");
                String preName = sc.next();
                //3.判断三：让用户确认被转账人姓名
                if (name1.startsWith(preName)) {
                    while (true) {
                        System.out.println("请输入转账的金额" + "（您最多可以转账：" + account.getMoney() + "元）：");
                        double transferAmount = sc.nextDouble();
                        //4.判断四：判断转账金额是否大于余额
                        if (transferAmount <= account.getMoney()) {
                            account.setMoney(account.getMoney() - transferAmount);
                            account1.setMoney(account1.getMoney() + transferAmount);
                            System.out.println("转账成功！你的余额为：" + account.getMoney());
                            return;
                        } else {
                            System.out.println("余额不足！");
                        }
                    }
                } else {
                    System.out.println("你输入的对方信息有误！");
                }
            } else {
                System.out.println("该卡号不存在请重新输入！");
            }
        }
    }

    /**
     * 修改密码
     *
     * @param account
     */
    private static void changePassword(Account account, Scanner sc) {
        while (true) {
            System.out.println("请输入当前密码进行认证：");
            String password1 = sc.next();
            if (password1.equals(account.getPassword())) {
                while (true) {
                    System.out.println("请输入新密码：");
                    String password2 = sc.next();
                    System.out.println("请确认新密码：");
                    String password3 = sc.next();
                    if (password2.equals(password3)) {
                        account.setPassword(password2);
                        System.out.println("修改成功！");
                        return;
                    } else {
                        System.out.println("两次密码不一致！");
                    }
                }
            } else {
                System.out.println("密码错误！请重新确认！");
            }
        }
    }

    /**
     * 注销账号
     *
     * @param account
     * @param sc
     */
    private static void logout(ArrayList<Account> accounts, Account account, Scanner sc) {
        while (true) {
            System.out.println("请您输入密码确认注销:");
            String password = sc.next();
            if (password.equals(account.getPassword())) {
                accounts.remove(account);
                System.out.println("注销成功！");
                break;
            } else {
                System.out.println("密码错误！");
            }
        }
    }
}

有问题请指出！