code: public static Double getLearningRate(MultiLayerNetwork net, int layerNumber) {
          Layer l = net.getLayer(layerNumber).conf().getLayer();
          int iter = net.getIterationCount();
          int epoch = net.getEpochCount();
          if (l instanceof BaseLayer) {
              BaseLayer bl = (BaseLayer) l;
              IUpdater u = bl.getIUpdater();
              if (u != null && u.hasLearningRate()) {
                  double d = u.getLearningRate(iter, epoch);
                  if (Double.isNaN(d)) {
                      return null;
                  }
                  return d;
              }
              return null;
          }
          return null;
      }
docs: Get the current learning rate, for the specified layer, fromthe network.
  Note: If the layer has no learning rate (no parameters, or an updater without a learning rate) then null is returned
  
  @param net         Network
  @param layerNumber Layer number to get the learning rate for
  @return Learning rate for the specified layer, or null