观察者模式实例

定义对象间的一种一对多依赖关系，使得每当一个对象改变状态，则其相关依赖的对象都能得到通知并被自动更新．

 定义两个接口：

观察者接口（提供更新等操作的方法）

package DesignPattern.ObserverPattern;

public interface AlarmListener {
 public void  alarm();

}

被观察者接口：（提供注册观察者实现类的方法，提供将改变通知观察者实现类的方法）

package DesignPattern.ObserverPattern;

public interface SensorInterface {
 public void register(AlarmListener al);
 public void soundTheAlarm();
}

具体被观察者定义：

package DesignPattern.ObserverPattern;

import java.util.Enumeration;
import java.util.Vector;

/**
 * 传感器系统
 *
 */
public class SensorSystem implements SensorInterface {
 Vector v=new Vector();
 /**
  *  注册监听者
  */
 public void register(AlarmListener al) {
  
  v.addElement(al);
 }
 /**
  * 发送告警
  */
 public void soundTheAlarm() {
  Enumeration e=v.elements();
  while(e.hasMoreElements()){
   AlarmListener al=null;
   al=(AlarmListener)e.nextElement();
   al.alarm();
  }
 } }

观察者实现类：

package DesignPattern.ObserverPattern;

public class AutoDefense implements AlarmListener{

 public void alarm() {
  System.out.println("********发现威胁*******");
  try {
   Thread.sleep(1000);
  } catch (InterruptedException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
  System.out.println(" 开始启动自动防御系统......");
  try {
   Thread.sleep(1000);
  } catch (InterruptedException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
  System.out.println("********检测到入侵源是一队恐怖分子*****");
  try {
   Thread.sleep(1000);
  } catch (InterruptedException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
 }

}

package DesignPattern.ObserverPattern;

public class Gun implements AlarmListener {

 public void alarm() {
  try {
   Thread.sleep(1000);
  } catch (InterruptedException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
  System.out.println("武器瞄准中......");
  try {
   Thread.sleep(2000);
  } catch (InterruptedException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
  System.out.println("***开枪***");
  try {
   Thread.sleep(2000);
  } catch (InterruptedException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
  System.out.println("恐怖分子已经全部击毙");
 }}

测试类:

package DesignPattern.ObserverPattern;

import DesignPattern.ObserverPattern.AlarmListener;
import DesignPattern.ObserverPattern.SensorSystem;
import DesignPattern.ObserverPattern.SensorInterface;;
public class ClientTest {
 
 public static void main(String[] args){
  SensorInterface sensor=new SensorSystem();
  sensor.register(new AutoDefense());
  sensor.register(new Gun());
  sensor.soundTheAlarm();
 }
 
 
 
}