表达公式
注册者 + 订阅者 = 观察者模式
设计气象站
气象站接口
/**
** 布告板
** @author lollipop
** @since 2019/11/24
**/
public interface DisplayElement {
/** 显示 **/
void display();
}
/**
* 观察者
* @author lollipop
* @since 2019/11/24
*/
public interface Observer {
/**
* 更新
* @param temperature
* @param humidity
* @param pressure
*/
void update(float temperature,float humidity,float pressure);
}
/**
* 主题接口
* @author lollipop
* @since 2019/11/24
*/
public interface Subject {
/**
* 注册
*/
void registerObserver(Observer o);
/**
* 注销
*/
void removeObserver(Observer o);
/**
* 通知
*/
void notifyObserver();
}
气象实现
/**
* @author lollipop
* @since 2019/11/24
*/
@Data
public class CurrentConditionsDisplay implements Observer, DisplayElement {
/**
* 温度
*/
private float temperature;
/**
* 湿度
*/
private float humidity;
/**
* 天气数据
*/
private Subject weatherData;
public CurrentConditionsDisplay(Subject weatherData) {
this.weatherData = weatherData;
weatherData.registerObserver(this);
}
/**
* 显示
*/
public void display() {
System.out.println("Current conditions: " + temperature
+ "F degrees and " + humidity + "% humidity");
}
/**
* 更新
* @param temperature
* @param humidity
* @param pressure
*/
public void update(float temperature, float humidity, float pressure) {
this.humidity = humidity;
this.temperature = temperature;
display();
}
}
/**
* @author lollipop
* @since 2019/11/24
*/
public class ForecastDisplay implements Observer, DisplayElement {
private float temperature;
private float humidity;
private float pressure;
/**
* 天气数据
*/
private Subject weatherData;
/**
* 显示
*/
public void display() {
if (this.pressure < 10.0f) {
System.out.println("晴天");
} else if (this.pressure >= 10.0f && this.pressure < 50.0f) {
System.out.println("多云");
} else {
System.out.println("下雨");
}
}
public ForecastDisplay(Subject weatherData) {
this.weatherData = weatherData;
weatherData.registerObserver(this);
}
/**
* 更新
*
* @param temperature
* @param humidity
* @param pressure
*/
public void update(float temperature, float humidity, float pressure) {
this.temperature = temperature;
this.humidity = humidity;
this.pressure = pressure;
this.display();
}
}
/**
* @author lollipop
* @since 2019/11/24
*/
public class StatisticsDisplay implements Observer, DisplayElement {
private float maxTemperatures = 0.00f;
private float minTemperatures = 0.00f;
private int count = 0;
private float totalTemperatures = 0.00f;
private float avgTemperatures = 0.00f;
/**
* 天气数据
*/
private Subject weatherData;
/**
* 显示
*/
public void display() {
System.out.println("maxTemperatures: " + maxTemperatures);
System.out.println("minTemperatures: " + minTemperatures);
System.out.println("avgTemperatures: " + avgTemperatures);
}
public StatisticsDisplay(Subject weatherData) {
this.weatherData = weatherData;
weatherData.registerObserver(this);
}
/**
* 更新
*
* @param temperature
* @param humidity
* @param pressure
*/
public void update(float temperature, float humidity, float pressure) {
if (this.maxTemperatures < temperature) {
this.maxTemperatures = temperature;
}
if (this.minTemperatures == 0.00f) {
this.minTemperatures = temperature;
} else if (this.minTemperatures > temperature) {
this.minTemperatures = temperature;
}
if (temperature > 0) {
totalTemperatures += temperature;
avgTemperatures = totalTemperatures / ++count;
}
this.display();
}
}
/**
* @author lollipop
* @since 2019/11/24
*/
@Data
public class WeatherData implements Subject {
/**
* 注入观察者
*/
List<Observer> observers = new ArrayList<Observer>(5);
/**
* 温度
*/
private float temperature;
/**
* 湿度
*/
private float humidity;
/**
* 气压
*/
private float pressure;
public WeatherData() {
}
/**
* 注册
*
* @param o
*/
public void registerObserver(Observer o) {
observers.add(o);
}
/**
* 注销
*
* @param o
*/
public void removeObserver(Observer o) {
int i = observers.indexOf(o);
if (i >= 0) {
observers.remove(o);
}
}
/**
* 通知
*/
public void notifyObserver() {
for (Observer one : observers) {
one.update(temperature, humidity, pressure);
}
}
/**
* 通知观察者
*/
public void measurementsChanged() {
notifyObserver();
}
/**
* 设置数据
*
* @param temperature
* @param humidity
* @param pressure
*/
public void setMeasurements(float temperature, float humidity, float pressure) {
this.temperature = temperature;
this.humidity = humidity;
this.pressure = pressure;
measurementsChanged();
}
}
气象站运行
/**
* @author lollipop
* @since 2019/11/25
*/
public class WeatherStation {
public static void main(String[] args) {
WeatherData weatherData = new WeatherData();
CurrentConditionsDisplay conditionsDisplay = 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);
}
}
运行结果
Current conditions: 80.0F degrees and 65.0% humidity
maxTemperatures: 80.0
minTemperatures: 80.0
avgTemperatures: 80.0
多云
Current conditions: 82.0F degrees and 70.0% humidity
maxTemperatures: 82.0
minTemperatures: 80.0
avgTemperatures: 81.0
多云
Current conditions: 78.0F degrees and 90.0% humidity
maxTemperatures: 82.0
minTemperatures: 78.0
avgTemperatures: 80.0
多云
总结
- 需要List集合保存注册者
- 轮询注册者列表，动态调用注册者更新方法