java jdk 观察者模式_JDK观察者模式实现Observer Observable

JDK提供了观察者模式的实现类java.util.Observer,java.util.Observable.

java.util.Observer为观察者。

java.util.Observable观察物。

1.观察物

Java代码

package observer;

import java.util.Observable;

public class Publisher extends Observable {

private String magazineName;

public String getMagazineName() {

return magazineName;

}

public void publish(String magazineName) {

this.magazineName = magazineName;

setChanged();// set the changed signal

notifyObservers();// notify all the observers

}

}

package observer;

import java.util.Observable;

public class Publisher extends Observable {

private String magazineName;

public String getMagazineName() {

return magazineName;

}

public void publish(String magazineName) {

this.magazineName = magazineName;

setChanged();// set the changed signal

notifyObservers();// notify all the observers

}

}

2.观察者

Java代码

package observer;

import java.util.Observable;

import java.util.Observer;

public class Reader implements Observer {

// when the observable changed ,

// it will notify all the observers and this method will be invoke

@Override

public void update(Observable o, Object arg) {

if(o instanceof Publisher){

Publisher p = (Publisher) o;

System.out.println("i want to read magazine. " + p.getMagazineName());

}

}

}

package observer;

import java.util.Observable;

import java.util.Observer;

public class Reader implements Observer {

// when the observable changed ,

// it will notify all the observers and this method will be invoke

@Override

public void update(Observable o, Object arg) {

if(o instanceof Publisher){

Publisher p = (Publisher) o;

System.out.println("i want to read magazine. " + p.getMagazineName());

}

}

}

3.测试类

Java代码

package observer;

public class Main {

public static void main(String[] args) {

// create observer

Reader reader=new Reader();

// create observable

Publisher publisher = new Publisher();

// add observer

publisher.addObserver(reader);

// observable do some action

publisher.publish("I am antlove.");

}

}