备忘录模式，在不破坏对象封装的情况下，获取对象状态并将其保存下来。

比如游戏关卡的存档。

 

 

 

游戏状态类

通过saveStatefToMemento（）方法存储状态

public class Originator {    //攻击力    private int aggressivity;    //防御力    private int defense;    //关卡    private int checkpoint;        public Originator(int aggressivity, int defense, int checkpoint) {        super();        this.aggressivity = aggressivity;        this.defense = defense;        this.checkpoint = checkpoint;    }    public int getAggressivity() {        return aggressivity;    }    public int getDefense() {        return defense;    }    public int getCheckpoint() {        return checkpoint;    }        public void setAggressivity(int aggressivity) {        this.aggressivity = aggressivity;    }    public void setDefense(int defense) {        this.defense = defense;    }    public void setCheckpoint(int checkpoint) {        this.checkpoint = checkpoint;    }    public void setAll(int aggressivity, int defense, int checkpoint) {        this.aggressivity = aggressivity;        this.defense = defense;        this.checkpoint = checkpoint;    }    //保存状态    public Memento saveStatefToMemento() {
    //使用一个Memento类保存状态，可以保证Originator的封装性        return new Memento(aggressivity, defense, checkpoint);    }    //获取状态    public void getStateFromMemento(Memento memento) {        this.aggressivity = memento.getAggressivity();        this.defense = memento.getDefense();        this.checkpoint = memento.getCheckpoint();    }        @Override    public String toString() {        return "Originator [aggressivity=" + aggressivity + ", defense=" + defense + ", checkpoint=" + checkpoint + "]";    }    }

 

 

保存游戏状态的类

该类的属性时根据Originator 类的属性设置的，

通过该类保存游戏状态，可以保证原有类的封装性。

public class Memento {    //攻击力    private int aggressivity;    //防御力    private int defense;    //关卡    private int checkpoint;    public Memento(int aggressivity, int defense, int checkpoint) {        super();        this.aggressivity = aggressivity;        this.defense = defense;        this.checkpoint = checkpoint;    }        public int getAggressivity() {        return aggressivity;    }        public int getDefense() {        return defense;    }        public int getCheckpoint() {        return checkpoint;    }}

 

 

获取存储状态的类

import java.util.HashMap;import java.util.Map;public class CareTaker {    private Map
     
       mementosMap = new HashMap
      
       ();        public void add(String keepInTheArchivesName,Memento memento) {        mementosMap.put(keepInTheArchivesName, memento);    }        public Memento get(String keepInTheArchivesName) {        return mementosMap.get(keepInTheArchivesName);    }}
      
     

 

Main

public class Main {    public static void main(String[] args) {        Originator originator = new Originator(0, 0, 0);        CareTaker careTaker = new CareTaker();                originator.setAll(100,50,1);        originator.setAll(200,70,2);        careTaker.add("存档一(已过第二关)",originator.saveStatefToMemento());        originator.setAll(400,100,3);        careTaker.add("存档一(已过第三关)",originator.saveStatefToMemento());        originator.setAll(500,150,4);                System.out.println("current:" + originator);                System.out.println("获取存档一状态");        originator.getStateFromMemento(careTaker.get("存档一(已过第二关)"));        System.out.println(originator);        System.out.println("获取存档二状态");        originator.getStateFromMemento(careTaker.get("存档一(已过第三关)"));        System.out.println(originator);            }}

运行结果： current:Originator [aggressivity=500, defense=150, checkpoint=4]获取存档一状态Originator [aggressivity=200, defense=70, checkpoint=2]获取存档二状态Originator [aggressivity=400, defense=100, checkpoint=3]

 

参考资料：