Java观察者模式
import java.util.ArrayList;
import java.util.List;
interface Subject {
void register(Observer observer);
void unregister(Observer observer);
void notifyObservers(String message);
}
class ConcreteSubject implements Subject {
private List<Observer> observers = new ArrayList<>();
private String message;
@Override
public void register(Observer observer) {
observers.add(observer);
}
@Override
public void unregister(Observer observer) {
observers.remove(observer);
}
@Override
public void notifyObservers(String message) {
this.message = message;
for (Observer observer : observers) {
observer.update(message);
}
}
}
interface Observer {
void update(String message);
}
class ConcreteObserver implements Observer {
private String name;
public ConcreteObserver(String name) {
this.name = name;
}
@Override
public void update(String message) {
System.out.println(name + " received message: " + message);
}
}
public class Test {
public static void main(String[] args) {
Subject subject = new ConcreteSubject();
Observer observer1 = new ConcreteObserver("Observer 1");
Observer observer2 = new ConcreteObserver("Observer 2");
subject.register(observer1);
subject.register(observer2);
subject.notifyObservers("Hello World!");
subject.unregister(observer1);
subject.notifyObservers("Hello Java!");
}
}
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