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Observers.java
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Observers.java
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import java.util.ArrayList;
public class Observers {
public static void main(String[] args) {
ConcreteSubject s = new ConcreteSubject();
ConcreteObserver o1 = new ConcreteObserver("o1");
ConcreteObserver o2 = new ConcreteObserver("o2");
s.registerObserver(o1); // 注册 o1
s.registerObserver(o2); // 注册 o2
s.notifyObservers("info1"); // 向观察者通知消息
System.out.println("remove observer o1");
s.removeObserver(o1); // 移除 o1
s.notifyObservers("info2"); // 再向观察者通知消息
}
}
interface Subject {
void registerObserver(Observer o);
void removeObserver(Observer o);
void notifyObservers(String info);
}
interface Observer {
void update(String info);
}
class ConcreteSubject implements Subject {
private final ArrayList<Observer> observers;
public ConcreteSubject() {
observers = new ArrayList();
}
public void registerObserver(Observer o) {
observers.add(o);
}
public void removeObserver(Observer o) {
observers.remove(o);
}
public void notifyObservers(String info) {
for (Observer o: observers) {
o.update(info);
}
}
}
class ConcreteObserver implements Observer {
private final String name;
public ConcreteObserver(String name) {
this.name = name;
}
public void update(String info) {
System.out.println(this.name + " get info: " + info);
}
}