备忘录模式Memento保存和回复内部状态

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。这样以后就可将该对象恢复到原先保存的状态。

public interface Memento {

}

public class Originator {
private String state = "";

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

public void setMemento(Memento memento) {
MementoImpl mementoImpl = (MementoImpl)memento;
this.state = mementoImpl.getState();
}

private static class MementoImpl implements Memento {
private String state = "";
public MementoImpl(String state) {
this.state = state;
}
public String getState() {
return state;
}
}
}

public class Caretaker {
private Memento memento = null;
public void saveMemento(Memento memento) {
this.memento = memento;
}
public Memento retriveMememto() {
return this.mememto;
}
}