java观察者模式

观察者模式：定义对象间的一种一对多的依赖关系，当一个对象的状态发生改变时，所有依赖它的对象都得到通知并自动更新。

 

package observer;public interface Subject {public void register(Observer observer);public void remove(Observer observer);public void notifiedObserver();}public interface Observer {public void update(float temp, float humidity, float pressure);}public class WeatherDate implements Subject {private float temp;private float humidity;private float pressure;private List list = null;public WeatherDate(){list = new ArrayList();}public void register(Observer observer) {list.add(observer);}public void remove(Observer observer) {int i = list.indexOf(observer);if (i >= 0) {list.remove(i);}}public void notifiedObserver() {for (int i = 0; i < list.size(); i++) {Observer observer = (Observer) list.get(i);observer.update(temp, humidity, pressure);}}public void changeDate() {notifiedObserver();}public void setMeasure(float temp, float humidity, float pressure) {this.temp = temp;this.humidity = humidity;this.pressure = pressure;changeDate();}}public class CurrentConditionsDisplay implements Observer {private float temp;private float humidity;private float pressure;private WeatherDate wd ;public CurrentConditionsDisplay(WeatherDate wd){this.wd = wd;wd.register(this);}public void update(float temp, float humidity, float pressure) {this.temp = temp;this.humidity = humidity;this.pressure = pressure; display();}public void display(){System.out.println("CurrentConditionsDisplay------>temp : " + temp + " humidity : " + humidity + " pressure : " + pressure);}}public class YesterdayConditionDisplay implements Observer {private float temp;private float humidity;private float pressure;private WeatherDate wd ;public YesterdayConditionDisplay(WeatherDate wd){this.wd = wd;wd.register(this);}public void update(float temp, float humidity, float pressure) {this.temp = temp;this.humidity = humidity;this.pressure = pressure;display();}public void display(){System.out.println("YesterdayConditionDisplay------>temp : " + temp + " humidity : " + humidity + " pressure : " + pressure);}}public class WeatherStation {public static void main(String[] args) {WeatherDate weatherdate = new WeatherDate();CurrentConditionsDisplay condition = new CurrentConditionsDisplay(weatherdate);YesterdayConditionDisplay ycd = new YesterdayConditionDisplay(weatherdate);weatherdate.setMeasure(80, 65, 70);}}