package com.vince.observer;
public interface Observable {
 //注册为一个观察者 
 public void registerObserver(Observer observer);
 
 //取消观察者 
 public void removeObserver(Observer observer);
 
 //通知所有观察者更新信息 
 public void notifyObservers();
}

package com.vince.observer;
import java.util.Vector;

public class Cup implements Observable{
 //被观察者维护的一个观察者对象列表
 private Vector<Observer> vector = new Vector<Observer>();
 private float price;
 
 public Cup(float price){
  this.price = price;
 }
 
 public float getPrice() {
  return price;
 }
 public void setPrice(float price) {
  //修改价格时，通知所有观察者
  this.price = price;
  notifyObservers();
 }
 @Override
 public void registerObserver(Observer observer) {
  //注册观察者
  vector.add(observer);
 }
 @Override
 public void removeObserver(Observer observer) {
  //取消观察者
  vector.remove(observer);
 }
 @Override
 public void notifyObservers() {
  //实现通知所有的观察者对象
  for (Observer observer:vector) {
   observer.update(price);
  }
 }
}

package com.vince.observer;

public interface Observer {

  public void update(float price);5 

}

package com.vince.observer;
public class Person implements Observer{
 private String name;
 public Person(String name){
  this.name = name;
 }
 @Override
 public void update(float price) {
  System.out.println(name+"关注的杯子的价格已更新为："+price);
 }
}

package com.vince.observer;
public class Test {
 public static void main(String[] args) {
  //创建一个被观察者对象
  Cup doll = new Cup(3000);
  //创建两个观察者对象
  Person p1 = new Person("生命壹号");
  Person p2 = new Person("生命贰号");
  //注册成为一个观察者
  doll.registerObserver(p1);
  doll.registerObserver(p2);
  
  System.out.println("第一轮促销：");
  doll.setPrice(2698);// 价格变动
  System.out.println("第二轮促销：");
  doll.setPrice(2299);//
  System.out.println("第三轮促销：");
  doll.setPrice(1998);
  
  doll.removeObserver(p2); //将生命二号移除
  System.out.println("第四轮促销：");
  doll.setPrice(1098);  
  
 }
}

package com.vince.observer2;
import java.util.Observable;

public class Cup extends Observable{
 private float price;
 
 public Cup(float price){
  this.price = price;
 }
 public float getPrice() {
  return price;
 }
 public void setPrice(float price) {
  this.price = price;
  this.setChanged();//通知，数据已改变
  this.notifyObservers();
 }
 
 
}

package com.vince.observer2;
import java.util.Observable;
import java.util.Observer;

public class Person implements Observer{
 private String name;
 public Person(String name){
  this.name = name;
 }
 @Override
 public void update(Observable o, Object arg) {
  if(o instanceof Cup){
   Cup cup = (Cup)o;
   System.out.println(name+"关注的杯子价格已更新为："+cup.getPrice());
  }
 }
}

package com.vince.observer2;
public class Test {
 public static void main(String[] args) {
  Cup cup = new Cup(3000);
  Person p1 = new Person("生命壹号");
  Person p2 = new Person("生命贰号");
  cup.addObserver(p1);
  cup.addObserver(p2);
  System.out.println("第一轮促销");
  cup.setPrice(2988);
  System.out.println("第二轮促销");
  cup.setPrice(2698);
  
  cup.deleteObserver(p2);
  System.out.println("第三轮促销");
  cup.setPrice(1998);
 }
}