《Head First 设计模式》观察者模式

观察者模式：在对象之间定义一对多的依赖，当一个对象改变通知，依赖他的对象都会收到通知，并自动更新

package headfirst.observer.weather;import java.util.*;public class WeatherStation {public static void main(String[] args) {WeatherData weatherData = new WeatherData();CurrentConditionsDisplay currentDisplay = new CurrentConditionsDisplay(weatherData);StatisticsDisplay statisticsDisplay = new StatisticsDisplay(weatherData);ForecastDisplay forecastDisplay = new ForecastDisplay(weatherData);weatherData.setMeasurements(80, 65, 30.4f);weatherData.setMeasurements(82, 70, 29.2f);weatherData.setMeasurements(78, 90, 29.2f);}}