设计模式--备忘录模式

实验 20：备忘录模式

本次实验属于模仿型实验，通过本次实验学生将掌握以下内容： 

1、理解备忘录模式的动机，掌握该模式的结构；

2、能够利用备忘录模式解决实际问题。

[实验任务]：多次撤销

改进课堂上的“用户信息操作撤销”实例，使得系统可以实现多次撤销（可以使用HashMap、ArrayList等集合数据结构实现）。

源代码

import java.util.ArrayList;
import java.util.List;

public class Caretaker
{

    private Memento memento;
    private List mementos = new ArrayList();

    //从备忘录中获取
    public Memento getMemento()
    {
        memento = mementos.get(mementos.size() - 1);
        mementos.remove(mementos.size() - 1);
        return memento;
    }

    //设置备忘录
    public void setMemento(Memento memento)
    {
        this.memento = memento;
        mementos.add(memento);
    }
}


class Memento
{
    private String account;
    private String password;
    private String telNo;

    public Memento(String account, String password, String telNo)
    {
        this.account = account;
        this.password = password;
        this.telNo = telNo;
    }

    public String getAccount()
    {
        return account;
    }

    public void setAccount(String account)
    {
        this.account = account;
    }

    public String getPassword()
    {
        return password;
    }

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

    public String getTelNo()
    {
        return telNo;
    }

    public void setTelNo(String telNo)
    {
        this.telNo = telNo;
    }
}

//用户信息
class UserInfoDTO
{
    private String account;
    private String password;
    private String telNo;

    public String getAccount()
    {
        return account;
    }

    public void setAccount(String account)
    {
        this.account = account;
    }

    public String getPassword()
    {
        return password;
    }

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

    public String getTelNo()
    {
        return telNo;
    }

    public void setTelNo(String telNo)
    {
        this.telNo = telNo;
    }

    public Memento saveMemento()
    {
        return new Memento(account, password, telNo);
    }

    public void restoreMemento(Memento memento)
    {
        this.account = memento.getAccount();
        this.password = memento.getPassword();
        this.telNo = memento.getTelNo();
    }

    public void show()
    {
        System.out.println("账户:" + this.account);
        System.out.println("密码:" + this.password);
        System.out.println("电话:" + this.telNo);
    }
}


public class Client
{
    public static void main(String[] args)
    {
        UserInfoDTO user = new UserInfoDTO();
        Caretaker c = new Caretaker();

        user.setAccount("张三");
        user.setPassword("123456");
        user.setTelNo("13000000000");
        System.out.println("状态一：");
        user.show();
        //保存备忘录
        c.setMemento(user.saveMemento());
        System.out.println("---------------------------");

        user.setPassword("111111");
        user.setTelNo("13100001111");
        System.out.println("状态二：");
        user.show();
        //保存备忘录
        c.setMemento(user.saveMemento());
        System.out.println("---------------------------");

        user.setPassword("333333");
        user.setTelNo("13333333333");
        System.out.println("状态三：");
        user.show();
        //保存备忘录
        c.setMemento(user.saveMemento());
        System.out.println("---------------------------");

        user.restoreMemento(c.getMemento());
        user.restoreMemento(c.getMemento());
        System.out.println("回到状态二：");
        user.show();
        System.out.println("---------------------------");
        user.restoreMemento(c.getMemento());
        System.out.println("回到状态一：");
        user.show();
        System.out.println("---------------------------");
    }
}

运行效果