状态模式

java中状态模式的一个小例子：

class Actor {public void act() {}}class HappyActor extends Actor {public void act() {System.out.println("HappyActor");}}class SadActor extends Actor {public void act() {System.out.println("SadActor");}}class Stage {/** * 初始状态 * */private Actor actor = new HappyActor();/** * 改变其状态 * */public void change() {actor = new SadActor();}/** * 显示其行为 * */public void performPlay() {actor.act();}}public class Transmogrify {public static void main(String[] args) {Stage stage = new Stage();/** * 显示初始状态信息 * */stage.performPlay();/** * 改变其状态 * */stage.change();/** * 打印状态改变后的信息 * */stage.performPlay();}}