WeatherData.java

package ObserverPattern.ManualExample;
import java.util.ArrayList;

public class WeatherData implements Subject{
    private ArrayList<Observer> observers;
    private float temperature;
    private float humidity;
    private float pressure;

    public WeatherData(){
        observers = new ArrayList<Observer>();
    }

    public void registerObserver(Observer o){
        observers.add(o);
    }

    public void removeObserver(Observer o){
        int i = observers.indexOf(o);
        if (i >= 0){
            observers.remove(i);
        }
    }

    public void notifyObservers(){
        for(Observer observer: observers){
            observer.update(temperature, humidity, pressure);
        }
    }

    public void measurementsChanged(){
        notifyObservers();
    }

    public void setMeasurements(float temperature, float humidity, float pressure){
        this.temperature = temperature;
        this.humidity = humidity;
        this.pressure = pressure;
        measurementsChanged();
    }

    // other WeatherData methods here

}