docs: public static DoubleMatrix getInstance(int rows, int cols, ItemSupplier s)
      {
          DoubleMatrix m = new DoubleMatrix(rows, cols);
          ItemConsumer c = m.consumer;
          for (int i = 0; i < rows; i++)
          {
              for (int j = 0; j < cols; j++)
              {
                  c.set(i, j, s.get(i, j));
              }
          }
          return m;
      }