Java设计模式：观察者模式

import java.util.ArrayList;

public abstract class Observable {
	private ArrayList observers = new ArrayList();

	public void addObserver(Observer observer) {
		observers.add(observer);
	}

	public void notifyObservers(Object object) {
		for (Observer observer : observers) {
			observer.update(this, object);
		}
	}
}

public interface Observer {
	void update(Observable observable, Object object);
}

Observer是观察者。Observable是被观察者。

 

public class Observer1 implements Observer {

	@Override
	public void update(Observable observable, Object object) {
		System.out.println("Observer1 update:" + object + "," + observable.toString());
	}
}

public class Observer2 implements Observer {
	@Override
	public void update(Observable observable, Object object) {
		System.out.println("Observer2 update:" + object + "," + observable.toString());
	}
}

 

public class Test {
	public static void main(String[] args) {
		try {
			Test test = new Test();
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	private class Target extends Observable {

	}

	public Test() {
		// 被观察者。
		Observable target = new Target();

		// 观察者。
		Observer observer1 = new Observer1();
		Observer observer2 = new Observer2();

		target.addObserver(observer1);
		target.addObserver(observer2);

		int count = 0;
		while (true) {
			target.notifyObservers(count++);

			try {
				Thread.sleep(1000);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		}
	}
}

输出：

Observer1 update:0,Test$Target@15db9742
Observer2 update:0,Test$Target@15db9742
Observer1 update:1,Test$Target@15db9742
Observer2 update:1,Test$Target@15db9742
Observer1 update:2,Test$Target@15db9742
Observer2 update:2,Test$Target@15db9742
Observer1 update:3,Test$Target@15db9742
Observer2 update:3,Test$Target@15db9742
Observer1 update:4,Test$Target@15db9742
Observer2 update:4,Test$Target@15db9742
Observer1 update:5,Test$Target@15db9742
Observer2 update:5,Test$Target@15db9742
Observer1 update:6,Test$Target@15db9742
Observer2 update:6,Test$Target@15db9742

......