java 观察者设计模式

package com.zkk;

public class Main {
public static void main(String[] args) {
Testmain main=new Testmain();
Observer1 t1=new Observer1();
Observer2 t2=new Observer2();
main.addObserver(t1);
main.addObserver(t2);

main.dosome();
//  main.notifyObservers();
//System.out.println("aaaaa");
}
}

package com.zkk;

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

public class Observer1 implements Observer{

@Override
public void update(Observable o, Object arg) {
System.out.println(arg);
}

}

package com.zkk;

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

public class Observer2 implements Observer {

@Override
public void update(Observable o, Object arg) {
System.out.println(arg);
}

}

package com.zkk;

import java.util.Observable;

public class Testmain extends Observable{
public void dosome(){
setChanged();
// notifyObservers();
notifyObservers("aa");
}
}