java基础：模拟ATM取款机

package com.atm;

import java.util.Scanner;

/**
 * ATM类实现
 * 
 * @author 向往的生活
 */
public class ATM {

    public static void main(String[] args) {
        String[] user = new String[2];
        String[] password = new String[2];
        double[] amount = new double[2];

        loginSelect(user, password, amount);

    }

    /**
     * 登录业务的菜单选择
     * 
     * @param user
     * @param password
     */
    public static void loginSelect(String[] user, String[] password,
            double[] amount) {
        System.out.println("#####欢迎#####");

        int n = 1;
        while (true) {
            System.out.println("A.开户");
            System.out.println("B.登录");
            System.out.println("C.退出");
            System.out.println("D.修改密码");

            Scanner scanner = new Scanner(System.in);
            System.out.println("选择菜单：");
            String number = scanner.nextLine();
            number = number.toUpperCase();

            char[] chr = number.toCharArray();
            switch (chr[0]) {
            case 'A':
                openAnAccount(user, password);
                loginSelect(user, password, amount);
                break;
            case 'B':
                int index = login(user, password);// 记录登录人的下标
                if (index != -1) {
                    select(user, password, amount, index);
                } else {
                    n++;// 登录3次失败，则退出
                    if (n == 3) {
                        break;
                    }
                }
                break;
            case 'C':
                System.out.println("退出ATM");
                System.exit(-1);
                break;
            case 'D':
                updatePassword(user, password);
                System.out.println("修改密码");
                break;
            default:
                System.out.println("录入的操作错误!");
                break;
            }
        }
    }

    /**
     * 核心业务菜单选择
     * 
     * @param user
     * @param password
     */
    public static void select(String[] user, String[] password,
            double[] amount, int index) {

        while (true) {
            System.out.println("###########您好:" + user[index] + "#########");
            System.out.println("A.存款");
            System.out.println("B.取款");
            System.out.println("C.转账");
            System.out.println("D.查询账户余额");
            System.out.println("E.返回主菜单");

            Scanner scanner = new Scanner(System.in);
            System.out.println("选择菜单：");
            String input = scanner.nextLine();
            input = input.toUpperCase();
            
            char chr = input.toCharArray()[0];

            switch (chr) {
            case 'A':
                saveMoney(user, amount, index);
                break;
            case 'B':
                getMoney(user, amount, index);
                break;
            case 'C':
                transferAccounts(user, amount, index);
                break;
            case 'D':
                query(user, amount, index);
                break;
            case 'E':
                loginSelect(user, password, amount);
                break;
            default:
                System.out.println("操作错误请重新输入!");
                break;
            }
        }
    }

    /**
     * 登录
     * 
     * @return
     */
    public static int login(String[] user, String[] password) {

        Scanner input = new Scanner(System.in);
        System.out.println("请输入用户名：");
        String userName = input.nextLine();

        System.out.println("请输入密码：");
        String pwd = input.nextLine();

        // 通过userName数据，找到user下标，
        int index = -1;
        for (int i = 0; i < user.length; i++) {
            if (user[i] == null) {
                System.out.println("请去开户,您没有注册卡号!");
                loginSelect(user, password, null);
                return -1;
            } else {
                if (user[i].equals(userName)) {
                    index = i;
                    break;
                }
            }
        }
        // 然后通过user下标找到password中相应的密码。
        if (password[index].equals(pwd)) {
            return index;
        } else {
            System.out.println("用户名或者密码输入错误，请从新输入！");
        }
        return -1;// 因为密码不匹配因此返回-1
    }

    /**
     * 开户
     * 
     * @return
     */
    public static void openAnAccount(String[] user, String[] password) {
        int index = -1;
        // 搜索下标
        for (int i = 0; i < user.length; i++) {
            if (user[i] == null) {
                index = i;
                break;
            }
        }
        if (index == -1) {// 如果存储空间满了,则提示联系管理员处理
            System.out.println("系统存储已经满了,请联系管理员处理!");
            return;
        }

        // 新增用于与密码
        Scanner scanner = new Scanner(System.in);
        System.out.println("输入登录名：");
        String loginName = scanner.nextLine();

        user[index] = loginName;
        System.out.println("输入密码：");
        String pwdValue = scanner.nextLine();

        password[index] = pwdValue;
    }

    /***************************************************************************
     * 查询账户余额
     * 
     * @return
     */
    public static void query(String[] user, double[] amount, int index) {
        System.out.println(user[index] + "您的余额为:" + amount[index]);
    }

    /**
     * 取款
     * 
     * @return
     */
    public static void getMoney(String[] user, double[] amount, int index) {
        
        System.out.println("A 100    B 200 ");
        System.out.println("C 300    D 500 ");
        System.out.println("E 1000   F 2000 ");
        System.out.println("G 其他金额       ");
        
        Scanner scanner = new Scanner(System.in);
        System.out.println("选择取款金额：");
        String money = scanner.nextLine();
        money = money.toUpperCase();
        
        
        double number = 0.0;
        char chr = money.toCharArray()[0];
        switch (chr) {
        case 'A':
            number = 100;
            break;
        case 'B':
            number = 200;
            break;
        case 'C':
            number = 300;
            break;
        case 'D':
            number = 500;
            break;
        case 'E':
            number = 1000;
            break;
        case 'F':
            number = 2000;
            break;
        case 'G':
            Scanner input = new Scanner(System.in);
            System.out.println("输入取款金额：");
            number = input.nextDouble();
            break;
        default:
            System.out.println("您输入的金额错误！");
            break;
        }

        // 检查存款的金额校验
        if (!checkMoney(number)) {
            return;
        }

        if(amount[index] < number) {
            System.out.println("您账户余额不足,不能取款！");
            return;
        }
        amount[index] = amount[index] - number;
        System.out.println("取款成功,余额为:" + amount[index]);// 显示余额
        return;
    }

    /**
     * 检查存款的金额校验
     * 
     * @param number
     * @return
     */
    public static boolean checkMoney(double number) {
        if (number < 100) {
            System.out.println("取款失败：只能取出大于等100的金额！");
            return false;
        }

        // 只能存入100的整数
        if (number % 100 != 0) {
            System.out.println("取款失败：只能取出100的整数！");
            return false;
        }
        return true;
    }

    /**
     * 存款
     */
    public static void saveMoney(String[] user, double[] amount, int index) {

        Scanner scanner = new Scanner(System.in);
        System.out.println("输入存款金额：");
        double number = scanner.nextDouble();

        // 检查存款的金额校验
        if (!checkMoney(number)) {
            return;
        }
        amount[index] = amount[index] + number;
        System.out.println("存款成功,余额为:" + amount[index]);// 显示余额
        return;
    }

    /**
     * 转账
     * 
     * @return
     */
    public static void transferAccounts(String[] user, double[] amount,
            int index) {
        int tragetIndex = -1;
        for (int i = 0; i < 3; i++) {
            tragetIndex = ifHaveUser(user);
            if (tragetIndex != -1) {
                break;
            } else {// 没找到相应的用户
                System.out.println("第" + (i + 1) + "次,您输入的用户不存在!");
            }
        }

        if (tragetIndex == -1) {
            System.out.println("超过3次返回上级菜单！");
            return;
        }

        if (tragetIndex == index) {// 如果下标相等提示您不能给自己转账
            System.out.println("您不能给自己转账");
        } else {
            for (int i = 0; i < amount.length; i++) {
                Scanner scanner = new Scanner(System.in);
                System.out.println("输入您的转账金额：");
                double tranAmount = scanner.nextDouble();

                // 检查存款的金额校验
                if (!checkMoney(tranAmount)) {
                    return;
                }
                if (tranAmount > amount[index]) {// 如果转账金额大于,账户余额提示
                    System.out.println("您余额不足!");
                    break;
                } else {
                    amount[index] = amount[index] - tranAmount;
                    amount[tragetIndex] = tranAmount;
                    break;
                }
            }
        }
        System.out.println("您的余额为:" + amount[index]);
    }

    /***************************************************************************
     * 
     * @return
     */
    public static int ifHaveUser(String[] user) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("输入转账用户：");
        String userName = scanner.nextLine();
        int index = -1;
        for (int i = 0; i < user.length; i++) {
            if (userName.equals(user[i])) {
                index = i;
            }
        }
        return index;
    }

    /***************************************************************************
     * 修改密码
     * 
     * @return
     */
    public static void updatePassword(String[] user, String[] password) {

        Scanner input = new Scanner(System.in);
        System.out.println("请输入用户名：");
        String userName = input.nextLine();
        while (true) {
            int index = -1;
            String oldPwd = null;
            for (int i = 0; i < user.length; i++) {//首先要找到当前用户
                if (userName.equals(user[i])) {
                    index = i;
                    oldPwd = password[i];
                }
            }
            if(index == -1) {
                System.out.println("还没有开户，请开户后再来修改密码！");
                return ;
            }
            System.out.println("请输入旧密码：");
            String inputOldPwd = input.nextLine();

            System.out.println("请输入新密码：");
            String newpwd = input.nextLine();
            
            System.out.println("请输入确认密码：");
            String confimpwd = input.nextLine();
            
            if(!inputOldPwd.equals(oldPwd)) {//如果输入的旧密码不等于新密码，则重新输入
                System.out.println("您输入的旧密码不正确！");
                continue;
            }
            if(!newpwd.equals(confimpwd)) {//新密码与确认密码不匹配
                System.out.println("新密码与确认密码不匹配!");
                continue;
            }
            password[index] = newpwd;
            System.out.println("密码修改成功!");
            break;
        }
    
    }
}