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Observer Design Pattern
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public interface Subject { | |
public void registerObserver(Observer o); | |
public void removeObserver(Observer o); | |
public void notifyObservers(); | |
} | |
public interface Observer { | |
public void update(float temp, float humidity, float pressure); | |
} | |
public interface DisplayElement { | |
public void display(); | |
} | |
public class WeatherData implements Subject { | |
private ArrayList<Observer> observers; | |
private float temp; | |
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) { observers.remove(o); } | |
public void notifyObservers() { | |
for (Observer o : observers) | |
o.update(temp, humidity, pressure); | |
} | |
public void mesurementsChanged() { notifyObservers(); } | |
public void setMeasurements(float temp, float humidity, float pressure) { | |
this.temp = temp; | |
this.humidity = humidity; | |
this.pressure = pressure; | |
} | |
} | |
public class CurrentConditionsDisplay implements Observer, DisplayElement { | |
private float temp; | |
private float humidity; | |
private Subject WeatherData; | |
public CurrentConditionsDisplay(Subject WeatherData) { | |
this.WeatherData = WeatherData; | |
WeatherData.removeObserver(this); | |
} | |
public void update(float temp, float humidity, float pressure) { | |
this.temp = temp; | |
this.humidity = humidity; | |
display(); | |
} | |
public void display() { | |
System.out.println("Current conditions: " + temp + "F and " + humidity + "%"); | |
} | |
} |
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