备忘录模式

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）。

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

public class Caretaker {
private List<Memento> list=new ArrayList<>();
public Memento getMemento() {
Memento mm=list.get(list.size()-2);
list.remove(list.size()-2);
return mm;
}
public void setMemento(Memento memento) {
list.add(memento);
}
}

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

}

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);
}
}
public class Client {
public static void main(String[] args) {
// TODO Auto-generated method stub
UserInfoDTO user=new UserInfoDTO();
Caretaker c=new Caretaker();
user.setAccount("zhangsan");
user.setPassword("123456");
user.setTelNo("1310000000");
System.out.println("状态一:");
user.show();
c.setMemento(user.saveMemento());
System.out.println("-----------------------------");
user.setPassword("111111");
user.setTelNo("1310001111");
System.out.println("状态二:");
user.show();
c.setMemento(user.saveMemento());
System.out.println("-----------------------------");
user.setPassword("zyx666");
user.setTelNo("15733333333");
System.out.println("状态三:");
user.show();
c.setMemento(user.saveMemento());
System.out.println("-----------------------------");
user.setPassword("777777");
user.setTelNo("15511111111");
System.out.println("状态四:");
user.show();
c.setMemento(user.saveMemento());
System.out.println("-----------------------------");
user.setPassword("666666");
user.setTelNo("17455555555");
System.out.println("状态五:");
user.show();
c.setMemento(user.saveMemento());
System.out.println("-----------------------------");
user.restoreMemento(c.getMemento());
System.out.println("回到状态四:");
user.show();
System.out.println("-----------------------------");
user.restoreMemento(c.getMemento());
System.out.println("回到状态三:");
user.show();
System.out.println("-----------------------------");
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("-----------------------------");
}

}