软件设计——备忘录模式之多次撤销

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）。

类图：

代码：

Caretaker.java

package com;

import java.util.ArrayList;

public class Caretaker {

	 private ArrayList<Memento> mementos= new ArrayList<Memento>();
	 
	 public Memento getMemento(int i)
	    
	 {
	        
		 return (Memento)mementos.get(i);    
	 }
	    
	 public void setMemento(Memento memento)
	    
	 {
	        
		 mementos.add(memento);
	    
	 }	    
	
}

UserInfoDTO.java

package com;
/*
 * 用户信息类
 */
public 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("Account:" + this.account);
	        System.out.println("Password:" + this.password);
	        System.out.println("TelNo:" + this.telNo);        
	    }
}

Memento.java

package com;

public 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;
	    }
}

Client.java

package com;



public class Client {

	public static void main(String a[]){
    UserInfoDTO user=new UserInfoDTO();
    Caretaker taker = new Caretaker();
  
    user.setAccount("zhangsan");
    user.setPassword("123456");
    user.setTelNo("13000000000");
    System.out.println("状态一：");
    taker.setMemento(user.saveMemento());
    user.show(); 
    System.out.println("---------------------------");
    
    user.setPassword("111111");
    user.setTelNo("13100001111");
    System.out.println("状态二：");    
    user.show();
    taker.setMemento(user.saveMemento());
    System.out.println("---------------------------");
        
    user.setPassword("222222");
    user.setTelNo("13100001111");
    System.out.println("状态三：");    
    user.show();
    System.out.println("---------------------------");
    
    System.out.println("回到状态二");
    user.restoreMemento(taker.getMemento(1));
    user.show();
    System.out.println("---------------------------");
    
    System.out.println("回到状态一");
    user.restoreMemento(taker.getMemento(0));
    user.show();
    
    System.out.println("---------------------------");
      
    }
}