企业门户网站的建设与实现,可以做配音兼职的网站,公司市场营销策划方案,可以免费做中考题的网站一、概述#xff1a;
1、定义#xff1a;观察者模式定义了一种一对多的依赖关系#xff0c;让多个观察者对象同时监听某一个主题对象。这个主题对象在状态发生变化时,会通知所有观察者对象#xff0c;使它们能够自动更新自己。
2、结构图#xff1a; public interface S…一、概述
1、定义观察者模式定义了一种一对多的依赖关系让多个观察者对象同时监听某一个主题对象。这个主题对象在状态发生变化时,会通知所有观察者对象使它们能够自动更新自己。
2、结构图 public interface Subject {void registerObserver(Observer observer);void unregisterObserver(Observer observer);void notifyObservers();
}
public interface Observer {void update();
}实现
import java.util.ArrayList;
import java.util.List;public class ConcreteSubject implements Subject {private ListObserver observers new ArrayList();private int state;public int getState() {return state;}public void setState(int state) {this.state state;notifyObservers();}Overridepublic void registerObserver(Observer observer) {observers.add(observer);}Overridepublic void unregisterObserver(Observer observer) {observers.remove(observer);}Overridepublic void notifyObservers() {for (Observer observer : observers) {observer.update();}}
}
public class ConcreteObserver implements Observer {private int observerState;private ConcreteSubject subject;public ConcreteObserver(ConcreteSubject subject) {this.subject subject;this.subject.registerObserver(this);}Overridepublic void update() {observerState subject.getState();System.out.println(Observer state updated: observerState);}
} 调用
public class Main {public static void main(String[] args) {ConcreteSubject subject new ConcreteSubject();ConcreteObserver observer1 new ConcreteObserver(subject);ConcreteObserver observer2 new ConcreteObserver(subject);subject.setState(10);// 输出// Observer state updated: 10// Observer state updated: 10subject.setState(20);// 输出// Observer state updated: 20// Observer state updated: 20subject.unregisterObserver(observer2);subject.setState(30);// 输出// Observer state updated: 30}
}
