場景：不同的人收到通知處理不一樣。

public interface WatcherObserver {//被通知的方法 public void update(WaterQualitySubject subject);//設置觀察人員的職務 public void setJob(String job);// 獲取觀察人員的職務 public String getJob(); }public class Watcher implements WatcherObserver{ private String job; //職務 public void update(WaterQualitySubject subject) {//這里采用的是拉的方式System.out.println(job+"獲取到通知，當前污染級別為："+subject.getPolluteLevel());} public String getJob() {return this.job;} public void setJob(String job) {this.job = job;} }public abstract class WaterQualitySubject {//用來保存注冊的觀察者對象 protected List<WatcherObserver> observers = new ArrayList<WatcherObserver>();//注冊觀察者對象 public void attach(WatcherObserver observer) {observers.add(observer);} public void detach(WatcherObserver observer) {observers.remove(observer);} public abstract void notifyWatchers(); //通知相應的觀察者對象 public abstract int getPolluteLevel();//獲取水質污染的級別 }//具體的水質監測對象 public class WaterQuality extends WaterQualitySubject{//污染的級別，0表示正常，1表示輕度污染，2表示中度污染，3表示高度污染private int polluteLevel = 0; //獲取水質污染的級別 public int getPolluteLevel() {return polluteLevel;}//當監測水質情況后，設置水質污染的級別 public void setPolluteLevel(int polluteLevel) {this.polluteLevel = polluteLevel;//通知相應的觀察者this.notifyWatchers();}//通知相應的觀察者對象 public void notifyWatchers() {//循環所有注冊的觀察者for(WatcherObserver watcher : observers){//開始根據污染級別判斷是否需要通知，由這里總控if(this.polluteLevel >= 0){//通知監測員做記錄if("監測人員".equals(watcher.getJob())){watcher.update(this);}}if(this.polluteLevel >= 1){//通知預警人員if("預警人員".equals(watcher.getJob())){watcher.update(this);}}if(this.polluteLevel >= 2){//通知監測部門領導if("監測部門領導".equals(watcher.getJob())){watcher.update(this);}}}}public class Client {public static void main(String[] args) {//創建水質主題對象WaterQuality subject = new WaterQuality();//創建幾個觀察者WatcherObserver watcher1 = new Watcher();watcher1.setJob("監測人員");WatcherObserver watcher2 = new Watcher();watcher2.setJob("預警人員");WatcherObserver watcher3 = new Watcher();watcher3.setJob("監測部門領導");//注冊觀察者subject.attach(watcher1);subject.attach(watcher2);subject.attach(watcher3);//填寫水質報告System.out.println("當水質為正常的時候------------------〉");subject.setPolluteLevel(0);System.out.println("當水質為輕度污染的時候---------------〉");subject.setPolluteLevel(1);System.out.println("當水質為中度污染的時候---------------〉");subject.setPolluteLevel(2);} }

總結

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