关于Java中的Observer模式

java内置的观察者模式:

   实际上是

1. 让subject扩展Observable(意即可观察者)类,Observable类已经定义好了register,delete,notify()等方法,直接使用即可,那可以在subject中移除自己的这些方法.有一点需注 意,在 notify()时必须先调用setChanged()方法,此方式表明状态更新.

 2.让observerDispaly继承Observer(java.util.Observer)接口,实现接口里的update()方法...

例子如下:

import java.util.Observable;
import java.util.Observer;
import object.oberver.dao.DisplayMent;
import object.oberver.dao1.NetPublisher;
public class Suberscriber_in_java implements Observer,DisplayMent {
  Observable observable;
  private String name;
  private String type;
  public Suberscriber_in_java(Observable observable){
   this.observable=observable;
   observable.addObserver(this);
  } 

 
 public void update(Observable o, Object arg) {
  if(o instanceof NetPublisher){
   NetPublisher np=(NetPublisher)o;
//拉出数据了
   this.name=np.getName();
   this.type=np.getType();
   display();
  }
 }
 public void display() {
  System.out.println(name+"   "+type+"更新了");
  
 }
}
import java.util.Observable;
import java.util.Observer;
public class NetPublisher extends Observable {
 private String name;
 private String type;
 public void setNewMessage(String name,String type){
  this.name=name;
  this.type=type;
  setChanged();
  notifyObservers();
     }
 //?用于拉的message
public String getName() {
 return name;
}
public String getType() {
 return type;
}
}
?写一个test
import object.oberver.dao1.NetPublisher;
import object.observer.impl.Suberscriber_in_java;
public class Test_in_java {
 public static void main(String[] args) {
      NetPublisher np=new NetPublisher();
      Suberscriber_in_java sij=new Suberscriber_in_java(np);
      np.setNewMessage("我改?了", "?型是哈哈");
 }
 
}