观察者模式

public class WeatherData extends Observable{
private float temperature; //温度
private float humidity; //湿度
private float pressure; //压强

public WeatherData(){}/** *温度变化时调用 */public void measurementsChanged(){    setChanged();    notifyObservers();}public void setWeatherChanged(float temperature,float humidity,float pressure){    this.pressure=pressure;    this.temperature=temperature;    this.humidity=humidity;    measurementsChanged();}public float getTemperature() {    return temperature;}public float getHumidity() {    return humidity;}public float getPressure() {    return pressure;}

}
public class CurrentConditionDisplay implements Observer {
@Override
public void update(Observable o, Object arg) {
if (o instanceof WeatherData){
WeatherData weatherData= (WeatherData) o;
weatherData.getHumidity();
System.out.println(“收到变化通知”);
}
}
}