备忘录模式

在不破坏封装性的前提下，获取并保存一个对象的内部状态，以便以后恢复它。

package com.strife.pattern.memento;

import java.util.ArrayList;
import java.util.List;

/**
 * @author mengzhenghao
 * @date 2022/6/4
 */
public class MementoCode {

    public static void main(String[] args) {
        Originator originator = new Originator();
        Caretaker caretaker = new Caretaker();

        originator.setState("State 1");
        System.out.println("Current state ===> " + originator.getState());
        caretaker.add(originator.saveStateMemento());
        originator.setState("State 2");
        System.out.println("Current state ===> " + originator.getState());
        originator.getStateFromMemento(caretaker.get(0));
        System.out.println("Current state ===> " + originator.getState());
    }
}

/** 备忘录角色 */
class Memento {

    /** 状态 */
    private String state;

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

    public String getState() {
        return state;
    }


}

/** 原始对象 */
class Originator {

    /** 状态 */
    private String state;

    public String getState() {
        return state;
    }

    public void setState(String state) {
        this.state = state;
    }

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

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

/** 守护者对象 */
class Caretaker {

    /** 管理备忘录 */
    private List<Memento> list = new ArrayList<>();

    public void add(Memento memento) {
        list.add(memento);
    }

    public Memento get(int index) {
        return list.get(index);
    }
}