第十八章 备忘录模式

备忘录模式（Memento）：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。这样以后就可以恢复该对象到原先的状态。

Caretaker负责不暴露Originator的内部细节，Memento负责备忘字段。用星姐的话----完美！\> <///

不足：角色状态要完整存储到备忘录对象中，如果状态数据很大很多，在资源消耗上，将非常耗内存。

/**
 * Created by hero on 16-4-5.
 */
public class Originator {
    private String state;

    public Memento createMemento(){
        return new Memento(state);
    }

    public void recoveryState(Memento memento){
        state = memento.getState();
    }

    public Originator() {
    }

    public Originator(String state) {
        this.state = state;
    }

    public String getState() {
        return state;
    }

    public void setState(String state) {
        this.state = state;
    }
}
/**
 * Created by hero on 16-4-5.
 */
public class Memento {
    private String state;

    public Memento(String state) {
        this.state = state;
    }

    public String getState() {
        return state;
    }

    //不能有set方法
}
/**
 * Created by hero on 16-4-5.
 */
public class Caretaker {
    private Memento memento;

    public Memento getMemento() {
        return memento;
    }

    public void setMemento(Memento memento) {
        this.memento = memento;
    }
}
public class Main {

    public static void main(String[] args) {
        Originator originator = new Originator();
        originator.setState("on");
        Caretaker caretaker = new Caretaker();
        caretaker.setMemento(originator.createMemento());
        originator.setState("off");
        originator.recoveryState(caretaker.getMemento());
    }
}