Observer pattern

1. 主题

package com.feng.design.observer;

import java.util.Observable;

public class WeatherData extends Observable {

private float temperature;

private float humidity;

private float presure;

public void measurementChanged() {

this.setChanged();

this.notifyObservers();

}

public void setMeasurement(float temperature, float humidity, float presure) {

this.temperature = temperature;

this.humidity = humidity;

this.presure = presure;

measurementChanged();

}

public float getTemperature() {

return temperature;

}

public float getHumidity() {

return humidity;

}

public float getPresure() {

return presure;

}

}

2. 观察者

package com.feng.design.observer;

import java.util.Observable;

import java.util.Observer;

public class CurrentConditionsDisplay implements Observer {

private float temperature;

private float humidity;

public CurrentConditionsDisplay(WeatherData weather) {

weather.addObserver(this);

}

@Override

public void update(Observable o, Object arg) {

if(o instanceof WeatherData) {

WeatherData weather = (WeatherData)o;

temperature = weather.getTemperature();

humidity = weather.getHumidity();

this.display();

}

}

public void display() {

System.out.println(this.toString() + "  tempeature:" + this.temperature + "  humidity:" + this.humidity);

}

}

3 Test

package com.feng.design.observer;

public class Test {

public static void main(String[] args) {

WeatherData weather = new WeatherData();

CurrentConditionsDisplay condition = new CurrentConditionsDisplay(weather);

weather.setMeasurement(12L, 111L, 333L);

CurrentConditionsDisplay condition1 = new CurrentConditionsDisplay(weather);

weather.setMeasurement(122L, 341L, 333L);

}

}

4 Console print

com.feng.design.observer.CurrentConditionsDisplay@4a5ab2  tempeature:12.0  humidity:111.0

com.feng.design.observer.CurrentConditionsDisplay@167d940  tempeature:122.0  humidity:341.0

com.feng.design.observer.CurrentConditionsDisplay@4a5ab2  tempeature:122.0  humidity:341.0