State Pattern(状态模式）

package state;interface TurnstileState {void coint(Turnstile t);void pass(Turnstile t);}class LockedTurnstileState implements TurnstileState{public void coint(Turnstile t) {t.setState(new UnlockedTurnstileState()); //should changed to t.setUnlocked();System.out.println("coint post,turnstile's state changed unlocked"); //should change it turnstile,as t.showMessage();}public void pass(Turnstile t) {System.out.println("Error!please put your coint ,or you can't pass!");//should change it turnstile}}class UnlockedTurnstileState implements TurnstileState{public void coint(Turnstile t) {System.out.println("Error!people have already post coint.");//should change it turnstile}public void pass(Turnstile t) {System.out.println("People pass! ");//should change it turnstilet.setState(new LockedTurnstileState());}}class Turnstile {private TurnstileState state=new LockedTurnstileState();public TurnstileState getState() {return state;}public void setState(TurnstileState state) {this.state = state;}public void coint(){this.state.coint(this);}public void pass(){this.state.pass(this);}}// <敏捷软件开发> P374public class StateApp {/** * @param args */public static void main(String[] args) {Turnstile turnstile =new Turnstile();turnstile.pass();turnstile.coint();turnstile.coint();turnstile.pass();turnstile.pass();}} 

相当于mvc 中的controller,不同的参数对应着不同的操作，视图。