Java内置的观察者模式

1.定义一个可观察者WeatherData,继承了java.util.Observable类

package pattern.javaObserver;

import java.util.Observable;

public class WeatherData extends Observable{

	private float temperature;
	private float humidity;
	private float pressure;

	public void measuarementsChanged(){
		setChanged();
		notifyObservers();
	}
	public void setWeatherData(float temperature,float humidity,float pressure){
		this.temperature = temperature;
		this.humidity = humidity;
		this.pressure = pressure;
		measuarementsChanged();
	}
	
	public float getTemperature() {
		return temperature;
	}
	
	public float getHumidity() {
		return humidity;
	}
	
	public float getPressure() {
		return pressure;
	}
}

2,.自定义一个定义显示接口DisplayElement。

package pattern.observer;

public interface DisplayElement {
	public void display();
}

3.定义一个观察者CurrentConditionDisplay，实现了java.util.Observer接口和自定义的显示接口DisplayElement。

package pattern.javaObserver;

import java.util.Observable;
import java.util.Observer;

import pattern.observer.DisplayElment;

public class CurrentConditionDisplay implements Observer , DisplayElement{
	Observable observable;
	private float temperature;
	private float humidify;
	
	public CurrentConditionDisplay(Observable o){
		this.observable = o;
		o.addObserver(this);
	}

	@Override
	public void display() {
		System.out.println("this is Current conditions:" + temperature +"F degrees and "+ humidify +"% humidity");
	}

	@Override
	public void update(Observable o, Object arg) {
		if(o instanceof WeatherData){
			WeatherData weatherData = (WeatherData) o;
			this.temperature = weatherData.getTemperature();
			this.humidify = weatherData.getHumidity();
			display();
		}
	}
}

4.测试程序

package pattern.javaObserver;

public class WeatherStation {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		WeatherData weatherData = new WeatherData();
		CurrentConditionDisplay c = new CurrentConditionDisplay(weatherData);
		weatherData.setWeatherData(50, 53, 50.3f);
		weatherData.setWeatherData(30, 33, 30.3f);
		weatherData.setWeatherData(40, 43, 40.3f);
	}

}

5.结果：
this is Current conditions:50.0F degrees and 53.0% humidity
this is Current conditions:30.0F degrees and 33.0% humidity
this is Current conditions:40.0F degrees and 43.0% humidity