备忘录模式

备忘录模式

备忘录（Memento）模式：在不破坏封装性的前提下，捕获一个对象的内部状态，并在该对象之外保存这个状态，以便以后当需要时能将该对象恢复到原先保存的状态。该模式又叫快照模式。

案例

每次玩游戏时从服务器读取存档，退出后保存存档

存档类：

public class GameRecoder {Integer id;Integer level;public GameRecoder(Integer id, Integer level) {this.id = id;this.level = level;}@Overridepublic String toString() {return "GameRecoder{" +"id=" + id +", level=" + level +'}';}
}

服务器：

public class GameServer {Map<Integer,GameRecoder> map = new HashMap<>();int cur = 0;{cur++;GameRecoder gameRecoder = new GameRecoder(cur, 1);map.put(cur,gameRecoder);}public void addRecord(Integer level){cur++;GameRecoder gameRecoder = new GameRecoder(cur, level);map.put(cur,gameRecoder);System.out.println("添加存档："+gameRecoder);}public GameRecoder getRecord(){System.out.println("读取存档："+map.get(cur));return map.get(cur);}
}

游戏：

public class MyGame {private Integer level;GameServer server = new GameServer();public void play(){GameRecoder record = server.getRecord();level = record.level;System.out.println("开始游戏，当前等级："+level);level++;}// 存档private void save(){server.addRecord(level);}public void exit(){System.out.println("退出游戏");save();}
}

测试：

public class Main {public static void main(String[] args) {MyGame myGame = new MyGame();myGame.play();myGame.exit();myGame.play();}
}