输出 备忘录模式的java代码

以下是备忘录模式的Java代码：

//备忘录类
class Memento {
private String state;

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

public String getState() {
return state;
}
}

//发起人类
class Originator {
private String state;

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

public String getState() {
return state;
}

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

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

//管理者类
class CareTaker {
private List<Memento> mementoList = new ArrayList<Memento>();

public void add(Memento state) {
mementoList.add(state);
}

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

//测试类
public class MementoPatternDemo {
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());
}
}