银行卡类

public class UserCard {
    private String cardNo;
    private String password;
    private String name;
    private double money;
    
    public UserCard(String cardNo,String password,String name)
    {
        this.cardNo=cardNo;
        this.password=password;
        this.name=name;
    }

    public double queryBalance()//查询余额
    {
        return money;
    }

    public double deposit(double money)//存钱
    {
        return this.money+=money;
    }

    public double withdraw(double money)//取钱
    {
        if(money>this.money)
        {
            return 0;
        }
        return this.money-=money;
    }

    public String getCardNo() {
        return cardNo;
    }

    public void setCardNo(String cardNo) {
        this.cardNo = cardNo;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public double getMoney() {
        return money;
    }

    public void setMoney(double money) {
        this.money = money;
    }
}

ATM类

import java.util.Scanner;

/**
 * Created by ttc on 17-12-29.
 */
public class ATM {
    Scanner n=new Scanner(System.in);
    private UserCard[] liberary=new UserCard[50];
    private int index;
    private UserCard currentCard;

    public void atmSystem()
    {
        System.out.println("欢迎来到ATM自动存取款系统");
        System.out.println("请选择你要使用的业务");
        System.out.println("--------------------");
        System.out.println("1.>取款.");
        System.out.println("2.>存款.");
        System.out.println("3.>查询信息.");
        System.out.println("4.>密码设置.");
        System.out.println("5.>退出系统.");
        int input=n.nextInt();
        if(input==1)
        {
            System.out.println("请输入您要提取的现金：");
            double withdraw=n.nextDouble();
            double result=currentCard.withdraw(withdraw);
            if(result==0)
            {
                System.out.println("余额不足");
            }
            else
            {
                System.out.println("提款成功！");
                System.out.println("您当前余额为："+currentCard.getMoney()+"元。");
            }
            atmSystem();
        }
        if(input==2)
        {
            System.out.println("请输入您要储存的现金：");
            double deposit=n.nextDouble();
            currentCard.deposit(deposit);
            System.out.println("存款成功！");
            System.out.println("您当前余额为："+currentCard.getMoney()+"元。");
            atmSystem();
        }
        if(input==3)
        {
            System.out.println("姓名："+currentCard.getName());
            System.out.println("卡号："+currentCard.getCardNo());
            System.out.println("余额："+currentCard.getMoney());
            atmSystem();
        }
        if(input==4)
        {
            System.out.println("请输入旧密码：");
            String oldPassword=n.next();
            if(oldPassword.equals(currentCard.getPassword()))
            {
                System.out.println("请输入新密码：");
                String newPassword=n.next();
                System.out.println("请再次输入新密码：");
                String newPassword2=n.next();
                if(newPassword.equals(newPassword2))
                {
                    System.out.println("密码修改成功！");
                    currentCard.setPassword(newPassword);
                    atmSystem();
                }
                else
                {
                    System.out.println("输入错误，请重新输入！");
                    atmSystem();
                }
            }
            else
            {
                System.out.println("输入错误！");
                atmSystem();
            }
        }
        if(input==5)
        {
            System.out.println("退出程序！");
        }
    }

    public void addUserCard(UserCard userCard)
    {
        if(index<liberary.length)
        {
            liberary[index]=userCard;
            index++;
        }
    }

    public void login()
    {
        System.out.println("请输入您的卡号：");
        String inputID=n.next();
        System.out.println("请输入您的密码：");
        String password=n.next();

        currentCard=checkCard(inputID,password);
        if(currentCard!=null)
        {
            System.out.println("登陆成功！");
            atmSystem();
        }
        else
        {
            System.out.println("账号或密码错误！");
        }
    }

    public UserCard checkCard(String strID,String password)
    {
        for(int i=0;i<index;i++)
        {
            if(strID.equals(liberary[i].getCardNo())&& password.equals(liberary[i].getPassword()))
            {
                return liberary[i];
            }
        }
        return null;
    }
}

Test类

public class ATMtest {
    public static void main(String[] args) {
        UserCard user1=new UserCard("001","000000","小李");
        user1.setMoney(2000);
        ATM atm=new ATM();
        atm.addUserCard(user1);
        atm.login();
    }
}