10.24

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。

 

[实验任务一]：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）。

实验要求：

1. 画出对应的类图；

2. 提交源代码；

3. 注意编程规范。

 

 

 

import java.util.ArrayList;

import java.util.List;

 

public class Caretaker

{

 

    private Memento memento;

    private List<Memento> mementos = new ArrayList<Memento>();

 

    //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("---------------------------");

    }

}