觀察者模式(Java實現)

標籤：

import java.util.ArrayList;import java.util.Iterator;/* 抽象觀察者類 */abstract class Observer {        public abstract void update();}/* 抽象被觀察主題類 */abstract class Subject{        private ArrayList obs_list = new ArrayList();        public void attach(Observer obs) {        obs_list.add(obs);    }        public void Detach(Observer obs) {        obs_list.remove(obs);    }        public void notifyObs() {        for (Iterator iter = obs_list.iterator(); iter.hasNext();) {            Observer obs = (Observer) iter.next();            obs.update();        }    }}/* 具體觀察者類 */class ConcreteObserver extends Observer {        private String obs_name;    private ConcreteSubject cc_subj;        public ConcreteObserver(String obs_name, ConcreteSubject cc_subj) {        this.obs_name = obs_name;        this.cc_subj = cc_subj;    }    public void update() {        if (cc_subj.getStatus() == 1) {            System.out.println("Boss come back, " + obs_name + " turn off screen!");        } else {            System.out.println("Boss go out, " + obs_name + " turn on screen!");        }    }}/* 具體觀察主題類 */class ConcreteSubject extends Subject {    private int status;    public ConcreteSubject(int status) {        this.status = status;    }        public int getStatus() {        return status;    }    public void setStatus(int status) {                if (status != this.status) {            this.status = status;            super.notifyObs();        }    }    }public class Observer_Test{    public static void main(String[] args) {                ConcreteSubject cc_sub = new ConcreteSubject(0);                ConcreteObserver cc_obs1 = new ConcreteObserver("E1", cc_sub);        ConcreteObserver cc_obs2 = new ConcreteObserver("E2", cc_sub);        ConcreteObserver cc_obs3 = new ConcreteObserver("E3", cc_sub);        cc_sub.attach(cc_obs1);        cc_sub.attach(cc_obs2);        cc_sub.attach(cc_obs3);                cc_sub.setStatus(1); //status changed to 1        System.out.println("---------------------------------------");        cc_sub.setStatus(0); //status changed to 0    }}

result：

Boss come back, E1 turn off screen!
Boss come back, E2 turn off screen!
Boss come back, E3 turn off screen!
---------------------------------------
Boss go out, E1 turn on screen!
Boss go out, E2 turn on screen!
Boss go out, E3 turn on screen!

觀察者模式(Java實現)