Memento Pattern(备忘录模式）

 

package memento;import java.util.*;class Origin {private String state;public Memento saveMemento(){return new Memento(this.state);}public void restoreState(Object o) {if(o instanceof Memento){this.state=((Memento)o).getState();}}public String getState() {return state;}public void setState(String state) {this.state = state;}public class Memento{private String state;public Memento(String state){this.state=state;}public String getState() {return state;}}}class Caretaker {List<Object> mementos=new ArrayList<Object>();public void addMemento(Object o){mementos.add(o);}public Object getMemento(int index){return mementos.get(index);}}public class MementoApp {/** * @param args */public static void main(String[] args) { Caretaker taker=new Caretaker(); Origin origin=new Origin(); origin.setState("good"); origin.setState("better"); taker.addMemento(origin.saveMemento()); origin.setState("best,you are right"); taker.addMemento(origin.saveMemento()); origin.setState("bad"); origin.restoreState(taker.getMemento(1)); System.out.println(origin.getState());}} 

 

参考：http://en.wikipedia.org/wiki/Memento_pattern