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. 提交源代码；
2. 注意编程规范。
package org.example.shiyan20;
public class main {
public static void main(String args[]) {
UserInfoDTO user = new UserInfoDTO();
Caretaker c = new Caretaker();
user.setAccount("zhangsan");
user.setPassword("123456");
user.setTelNo("130000");
System.out.println("状态一：");
user.show();
c.addMemento(user.saveMemento());
System.out.println("-----------------");
user.setPassword("111111");
user.setTelNo("130111");
System.out.println("状态二：");
user.show();
c.addMemento(user.saveMemento());
System.out.println("-----------------");
user.setPassword("222222");
user.setTelNo("130222");
System.out.println("状态三：");
user.show();
System.out.println("-----------------");
user.restoreMemento(c.preMemento());
System.out.println("回到状态二：");
user.show();
System.out.println("-----------------");
user.restoreMemento(c.preMemento());
System.out.println("回到状态一：");
user.show();
System.out.println("-----------------");
}
}
//Caretaker.java
package org.example.shiyan20;
public class Caretaker
{
private Memento[] array = null;
private int index;
private Memento memento;
public Memento getMemento()
{
return memento;
}
public void setMemento(Memento memento)
{
this.memento=memento;
}
public Caretaker(){
array = new Memento[10];
index = 0;
}
public void addMemento(Memento Memento){
array[index++] = Memento;
}
public Memento preMemento(){
Memento pop = null;
try {
pop = array[--index];
} catch (Exception e) {
e.printStackTrace();
}
return pop;
}
}
package org.example.shiyan20;
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;
}
}
package org.example.shiyan20;
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("账号是" + this.account);
System.out.println("密码是" + this.password);
System.out.println("电话是" + this.telNo);
}
}