一、我的理解
备忘录模式用于存储某个类在某一时刻的状态。
二、实现方式
另外创建一个类Memento用于保存目标类的状态信息，然后由另一类来存储和管理这一系列保存的状态
三、实例
Java实例
Originator类：原始类，对该类的状态进行保存
package com.study.dp.memento;
public class Originator {
private String state;
public String getState() {
return state;
}
public void setState(String state) {
this.state = state;
}
public Memento saveStateToMemento() {
return new Memento(state);
}
public void getStateFromMemento(Memento memento) {
this.state = memento.getState();
}
}Memento类：备忘录类，保存目标类的状态信息
package com.study.dp.memento;
public class Memento {
private String state;
public Memento(String state) {
super();
this.state = state;
}
public String getState() {
return state;
}
}CareTaker类：备忘录管理类，存储和管理备忘录
package com.study.dp.memento;
import java.util.ArrayList;
import java.util.List;
public class CareTaker {
private List<Memento> mementoList = new ArrayList<>();
public void add(Memento state) {
mementoList.add(state);
}
public Memento get(int index) {
return mementoList.get(index);
}
}Demo类：测试
package com.study.dp.memento;
public class Demo {
public static void main(String[] args) {
Originator originator = new Originator();
CareTaker careTaker = new CareTaker();
originator.setState("State #1");
originator.setState("State #2");
careTaker.add(originator.saveStateToMemento());
originator.setState("State #3");
careTaker.add(originator.saveStateToMemento());
originator.setState("State #4");
System.out.println("Current State: "+originator.getState());
originator.getStateFromMemento(careTaker.get(0));
System.out.println("First saved State: "+originator.getState());
originator.getStateFromMemento(careTaker.get(1));
System.out.println("Second saved State: "+originator.getState());
}
}
四、应用场景
