code: @Nullable
    public StorageTierView getNextTier(StorageTierView tierView) {
      int nextOrdinal = tierView.getTierViewOrdinal() + 1;
      if (nextOrdinal < mTierViews.size()) {
        return mTierViews.get(nextOrdinal);
      }
      return null;
    }
docs: Gets the next storage tier view.
  
  @param tierView the storage tier view
  @return the next storage tier view, null if this is the last tier view