code: private void checkColumnSize(Column<?> newColumn) {
          if (columnCount() != 0) {
              Preconditions.checkArgument(newColumn.size() == rowCount(),
                      "Column " + newColumn.name() +
                              " does not have the same number of rows as the other columns in the table.");
          }
      }
docs: Throws an IllegalArgumentException if the column size doesn't match the rowCount() for the table