定义：观察者模式定义了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，则所有依赖于它的对象都会得到通知并被自动更新
题目：某实验室欲建立一个实验室环境监测系统，能够显示实验室的温度、湿度以及洁净度等环境数据。当获取到最新的环境测量数据时，显示的环境数据能够更新。现采用观察者模式来开发该系统
import java.util.*;
interface Observer{
public void update(float temp,float humidity,float cleanness);}
interface Subject{
public void registerObserver(Observer o); //注册对主题感兴趣的观察者
public void removeObserver(Observer o); //删除观察者
public void notifyObservers(); //当主题发生变化时通知观察者
}
class EnvironmentData implements Subject{
private ArrayList observers;
private float temperature,humidity,cleanness;
public EnvironmentData(){observers=new ArrayList();}
public void registerObserver(Observer o){observers.add(o);}
public void removeObserver(Observer o){/代码省略/}
public void notifyObservers(){
for(int i=0;i<observers.size();i++){
Observer observer=(Observer)observers.get(i);
observer.update(temperature,humidity,cleanness);
}
}
public void measurementsChanged(){
notifyObservers();
}
public void setMeasurements(float temperature,float humidity,
float cleanness){
this.temperature=temperature;
this.humidity=humidity;
this.cleanness=cleanness;
measurementsChanged();
}
}
class CurrentConditionsDisplay implements Observer{
private float temperature;
private float humidity;
private float cleanness;
private Subject envData;
public CurrentConditionsDisplay(Subject envData){
this.envData=envData;
envData.registerObserver(this);
}
public void update(float temperature,float humidity,float cleaness){
this.temperature=temperature;
this.humidity=humidity;
this.cleanness=cleanness;
display();
}
public void display(){/代码省略/}
}
class EnvironmentMonitor{
public static void main(String[] args){
EnvironmentData envData=new EnvironmentData();
CurrentConditionsDisplay currentDisplay =new CurrentConditionDisplay(envData);
envData.setMeasurements(80,65,30.4f);
}
}
