java 观察者设计模式示范代码
时间: 2023-04-03 19:01:53 浏览: 81
以下是一个简单的 Java 观察者设计模式示范代码:
观察者接口:
public interface Observer {
void update(String message);
}
主题接口:
public interface Subject {
void registerObserver(Observer observer);
void removeObserver(Observer observer);
void notifyObservers(String message);
}
主题实现类:
import java.util.ArrayList;
import java.util.List;
public class ConcreteSubject implements Subject {
private List<Observer> observers = new ArrayList<>();
@Override
public void registerObserver(Observer observer) {
observers.add(observer);
}
@Override
public void removeObserver(Observer observer) {
observers.remove(observer);
}
@Override
public void notifyObservers(String message) {
for (Observer observer : observers) {
observer.update(message);
}
}
}
观察者实现类:
public class ConcreteObserver implements Observer {
private String name;
public ConcreteObserver(String name) {
this.name = name;
}
@Override
public void update(String message) {
System.out.println(name + " 收到消息:" + message);
}
}
使用示例:
public class ObserverDemo {
public static void main(String[] args) {
ConcreteSubject subject = new ConcreteSubject();
Observer observer1 = new ConcreteObserver("观察者1");
Observer observer2 = new ConcreteObserver("观察者2");
subject.registerObserver(observer1);
subject.registerObserver(observer2);
subject.notifyObservers("Hello World!");
subject.removeObserver(observer1);
subject.notifyObservers("Goodbye World!");
}
}
输出结果:
观察者1 收到消息:Hello World!
观察者2 收到消息:Hello World!
观察者2 收到消息:Goodbye World!