###问题描述
实现一个观察者模式，监听方法接受一个Integer参数，并且其打印出来###自己实现
public static void main(String[] args) { EventSource eventSource = new EventSource(); eventSource.register(new Listener()); eventSource.print(1);}interface Print { void print(Integer integer);}static class EventSource implements Print { private Set listeners = Sets.newCopyOnWriteArraySet(); public void print(Integer integer) { for (Print listener : listeners) { listener.print(integer); } } public void register(Print print) { listeners.add(print); }}static class Listener implements Print { public void print(Integer integer) { System.out.println(integer); }} ###使用JDK实现
public static void main(String[] args) { EventSource eventSource = new EventSource(); eventSource.addObserver(new Listener()); eventSource.print(1);}static class EventSource extends Observable { public void print(Integer integer) { setChanged(); notifyObservers(integer); }}static class Listener implements Observer { public void update(Observable o, Object arg) { System.out.println(arg); }} ###使用Guava
public static void main(String[] args) { EventBus eventBus = new EventBus(); eventBus.register(new Listener()); eventBus.post(1);}static class Listener { @Subscribe public void print(Integer integer) { System.out.println(integer); }}