类的封装，继承和多态 ： 声明银行账户类，成员变量包括账号、储户姓名、开户时间、身份证号码、存款余额等账户信息，成员方法包括开户、存款、取款、查询（余额、明细）、销户等操作。

import java.util.Scanner;
public class BankAccount
{
    private String Number;//账号
    private String Name;  //储户姓名
    private String OpenTime;//开户时间
    private String CardNumber;//省份证号码
    private double Balance;    //账户余额
    public BankAccount(String Number,String Name,String OpenTime,String CardNumber,double Balance)//构造方法.及开户
    {
        this.Number=Number;
        this.Name=Name;
        this.OpenTime=OpenTime;
        this.CardNumber=CardNumber;
        this.Balance=Balance;
        System.out.println("开户成功！\n"+this.Name+"欢迎您！");
    }
    protected void finalize()//账号销毁
    {
        System.out.println(this.Name+"您的账户已销毁！");
    }
    public void income(double money)//存款操作，参数为存入金额
    {
        if(money>0) {
            this.Balance = this.Balance + money;
            System.out.println("存款成功！");
        }
        else
            System.out.println("存款金额无效！存款失败！");
    }
    public void takeout(double money)//取款，参数为取款金额
    {
        if(money<=this.Balance) {
            this.Balance = this.Balance - money;
            System.out.println("取款成功！");
        }
        else
            System.out.println("余额不足！取款失败！");
    }
    public void ShowYuer()//显示余额
    {
        System.out.println("余额为:"+this.Balance);
    }
    public void Show()
    {
        System.out.println("你的账户信息为:\n账号\t开户时间\t身份证号码\n"+this.Number+"\t" +this.OpenTime+"\t"+this.CardNumber  );
    }
    public static void main(String[] args)
    {
        int j=1;
        BankAccount b=new BankAccount("0001231","张华","1999-2-8","230118198006051842",100);
        b.Show();
        System.out.println("请选择操作：0 退出，1 存款，2 取款，3 余额查询，4 销户");
        while(true)
        {
            Scanner cin=new Scanner(System.in);
            int i=cin.nextInt();
            switch(i)
            {
                case 0:
                    System.out.println("欢迎下次光临!");
                    System.exit(0);break;
                case 1:
                    System.out.println("请输入存款金额:");
                    double m1=cin.nextInt();
                    b.income(m1);
                    break;
                case 2:
                    System.out.println("请输入取款金额:");
                    double m2=cin.nextInt();
                    b.takeout(m2);
                    break;
                case 3:
                    b.ShowYuer();break;
                case 4:
                    b.finalize();break;
                default:
                    System.out.println("选择错误!");break;
            }
        }
    }
}