code: public void setRowSpec(int rowIndex, RowSpec rowSpec) {
          checkNotNull(rowSpec, "The row spec must not be null.");
          rowSpecs.set(rowIndex - 1, rowSpec);
      }
docs: Sets the RowSpec at the specified row index.
  
  @param rowIndex the index of the row to be changed
  @param rowSpec the RowSpec to be set
  @throws NullPointerException if {@code rowSpec} is {@code null}
  @throws IndexOutOfBoundsException if the row index is out of range