code: public static <V> DenseGrid<V> create(int rowCount, int columnCount) {
          return new DenseGrid<V>(rowCount, columnCount);
      }
docs: Creates an empty {@code DenseGrid} of the specified size.
  
  @param <V> the type of the value
  @param rowCount  the number of rows, zero or greater
  @param columnCount  the number of rows, zero or greater
  @return the mutable grid, not null