public class App {
   public static void main(String argv[]) {
     Sensor sensor = new Sensor();
     Display display = new Display();
     // register observer with observable class
     sensor.addObserver(display);
     // simulate measuring temperatures over time
     for(int i=0;i<10;i++) {
       sensor.takeReading();
       sensor.notifyObservers();
     }
   }
}