public void addMeasurementListener(MeasurementListener l){
  if (!measurementListeners.contains(l)) {
    measurementListeners.addElement(l);
  }
}

public void addMeasurementListener ( MeasurementListener l ) { if ( ! measurementListeners . contains ( l ) ) { measurementListeners . addElement ( l ) ; } }
request being informed when a new measurement is available .
