设计模式之二-----观察者模式

观察者模式由2部分组成   主题  和  观察者

1 主题接口

package com.observer;

/***
 * 
 * @author shasha
 * 观察者主题类
 */
public interface Subject {

	public void registObserver(Observer o);
	
	public void removeObserver(Observer o);
	
	public void notifyObservers();
}

 

2 天气预报主题 （实现了主题接口）

package com.observer;

import java.util.ArrayList;
/**
 * 
 * @author shasha
 * 主题实现类---天气预报主题
 */
public class WeatherData implements Subject {
	
	private ArrayList<Observer> observers;
	private float temperature;
	private float humidity;
	private float pressure;
	
	public WeatherData(){
		observers=new ArrayList<Observer>();
	}

	@Override
	public void notifyObservers() {
		// TODO Auto-generated method stub
		for(int i=0;i<observers.size();i++){
			Observer observer=observers.get(i);
			observer.update(temperature, humidity, pressure);
		}
	}

	@Override
	public void registObserver(Observer o) {
		// TODO Auto-generated method stub
		observers.add(o);
	}

	@Override
	public void removeObserver(Observer o) {
		// TODO Auto-generated method stub
		int i=observers.indexOf(o);
		if(i>=0){
			observers.remove(o);
		}
	}

	
	public void setMeasurements(float temperature,float humidity,float pressure){
		this.temperature=temperature;
		this.humidity=humidity;
		this.pressure=pressure;
		measurementsChanged();
	}
	
	public void measurementsChanged(){
		notifyObservers();
	}
}

 

 3 观察者接口

package com.observer;

/**
 * 
 * @author shasha
 * 观察者
 */
public interface Observer {

	public void update(float temp,float humidity,float pressure);
	
}

 

 

4 显示信息接口

package com.observer;

/***
 * 
 * @author shasha
 * 显示接口
 *
 */
public interface DisplayElement {

	public void display();
}

 

 

5 观察者实现类----天气预报显示版

package com.observer;
/***
 * 
 * @author duwan
 * 天气预报显示板
 */
public class CurrentConditionDisplay implements DisplayElement,Observer{

	private float temperature;
	private float humidity;
	private Subject weatherdate;
	
	public CurrentConditionDisplay(Subject weatherdata){
		this.weatherdate=weatherdata;
		weatherdata.registObserver(this);
	}
	@Override
	public void display() {
		// TODO Auto-generated method stub
		System.out.println("temperature: "+temperature+" F degress and"+humidity+"% humidity");
	}

	@Override
	public void update(float temp, float humidity, float pressure) {
		// TODO Auto-generated method stub
		this.temperature=temp;
		this.humidity=humidity;
		display();
	}

}

 6 测试程序 气象站

package com.observer;

/**
 * 
 * @author shasha
 * 气象站测试程序
 */
public class WeatherStation {

	public static void main(String[] args) {
		WeatherData weatherData=new WeatherData();
		CurrentConditionDisplay ccd=new CurrentConditionDisplay(weatherData);
		weatherData.setMeasurements(80, 65, 30.4f);
	}
}

 

 

--------针对需求 可以在

public void measurementsChanged(){
  notifyObservers();
 }

增加一个setChange（） 与java.util.Observser中一样 完成一定情况下才提醒观察者