java观察者模式

package observer;

import java.util.Observable;

//广播站
public class Radio extends Observable{
private String content;
public void broadcast(String content){
this.content = content;
//有新内容
setChanged();
//广播
notifyObservers();
}

public String getContent() {
return content;
}
public void setContent(String content) {
this.content = content;
}
}

package observer;

import java.util.Observable;
import java.util.Observer;

public class Reader implements Observer{
//持有广播的引用（手里拿着收音机）
Observable radio;
Reader(Observable radio){
this.radio = radio;
radio.addObserver(this);
}

//接收到广播，并且输出内容
@Override
public void update(Observable radio, Object arg1) {
Radio r = (Radio)radio;
System.out.println("get:"+r.getContent());
}

}

package observer;

public class Main {

public static void main(String[] args) {
//创建一个广播站
Radio r = new Radio();

//创建两个收听者
Reader reader1 = new Reader(r);
Reader reader2 = new Reader(r);

//广播站发通知
r.broadcast("testing...");
}

}