package observer;
/*** 观察主题*/
public interface Observable{public void addObserver(Observer observer);//添加观察者public void removeObserver(Observer observer);//移除观察者public void notifyObservers(WeatherData data);//通知所有观察者
}

package observer;
/*** 观察者*/
public interface Observer {public abstract void update(WeatherData data);
}

package observer;
/*** 天气数据*/
public class WeatherData {private float temperature;private float humidity;private float pressure;public WeatherData(){}public WeatherData(float temperature, float humidity, float pressure){this.temperature = temperature;this.humidity = humidity;this.pressure = pressure;}
}

package observer;
/*** 显示*/
public interface DisplayElement {void display();
}

package observer;
/*** 当前天气状况*/
public class CurrentConditionsDisplay implements DisplayElement, Observer {Observable observable;public CurrentConditionsDisplay(Observable observable) {this.observable = observable;}WeatherData data = new WeatherData();@Overridepublic void display() {System.out.println("当前的天气状况： " + "温度(℉)：" + data.getTemperature() + " " + "湿度：" + data.getHumidity() + " " +"气压：" + data.getPressure());}@Overridepublic void update(WeatherData data) {this.data = data;display();}
}

package observer;
/*** 天气统计**/
public class StatisticsDisplay implements DisplayElement, Observer {private Float average;private Float highest;private Float lowest;@Overridepublic void display() {System.out.println("天气统计：" +"平均温度(℉)：" + average + " " +"最高温度(℉)：" + highest + " " +"最低温度(℉)：" + lowest);}@Overridepublic void update(WeatherData data) {float temperature = data.getTemperature();average = null == average ? temperature : (average + temperature) / 2;highest = null == highest ? temperature : (highest > temperature ? highest : temperature);lowest = null == lowest ? temperature : (lowest > temperature ? temperature : lowest);display();}}

package observer;
/*** 天气预报*/
public class ForecastDisplay implements DisplayElement, Observer {private float pressure;@Overridepublic void update(WeatherData data) {pressure = data.getPressure();display();}@Overridepublic void display() {System.out.println("天气预测：" + forecast());}private static final float INFRABAR = 28.5f;//气压低就会下雨private String forecast(){return INFRABAR < pressure ? "明天不下雨" : "明天要下雨";}
}

package observer;
import java.util.ArrayList;
import java.util.List;
/*** 天气主题**/
public class Weather implements Observable {private List<Observer> observers = new ArrayList<>();;public void addObserver(Observer observer) {observers.add(observer);}public void removeObserver(Observer observer) {observers.remove(observer);}public void notifyObservers(WeatherData data) {for (Observer observer : observers)observer.update(data);}
}

package observer;
/*** 测试* @author Skysea**/
public class Client {public static void main(String[] args) {Observable observable = new Weather();Observer currentCondition = new CurrentConditionsDisplay(observable);Observer statistics = new StatisticsDisplay();Observer forecast = new ForecastDisplay();observable.addObserver(currentCondition);observable.addObserver(statistics);observable.addObserver(forecast);observable.notifyObservers(new WeatherData(80, 65, 30.4f));observable.notifyObservers(new WeatherData(82, 70, 29.2f));observable.notifyObservers(new WeatherData(78, 90, 25.1f));}
}

package observer;
/*** 测试2*/
public class Client2 {@Autowiredprivate Observable observable;public static void main(String[] args) {observable.notifyObservers(new WeatherData(80, 65, 30.4f));observable.notifyObservers(new WeatherData(82, 70, 29.2f));observable.notifyObservers(new WeatherData(78, 90, 25.1f));}
}