code: private void actionProducing(double extrp)
      {
          for (final ProducerListener listener : listeners)
          {
              listener.notifyProducing(currentObject);
          }
          for (final ProducibleListener listener : current.getFeature(Producible.class).getListeners())
          {
              listener.notifyProductionProgress(this);
          }
          progress += speed * extrp;
  
          // Production time elapsed
          if (progress >= steps)
          {
              progress = steps;
              state = ProducerState.PRODUCED;
          }
      }
docs: Action called from update production in producing state.
  
  @param extrp The extrapolation value.