摘要： import java.util.ArrayList;import java.util.List;//被观察者接口interface Watched{ public void addWatcher(Watcher watcher); public void removeWatcher(Watcher watcher); public void notifyAllWatchers(String str);}//被观察者实现类class ConcreteWatched implements Watched{ List<Watcher> watchers=new ArrayL... 阅读全文