code: public long order() {
          // A group may have a size larger than Integer.MAX_INTEGER
          // (2 ** 32 - 1) - for example sym(13) is larger.
          long total = 1;
          for (int i = 0; i < size; i++) {
              int sum = 0;
              for (int j = 0; j < size; j++) {
                  if (this.permutations[i][j] != null) {
                      sum++;
                  }
              }
              total *= sum;
          }
          return total;
      }
docs: Calculates the size of the group.
  
  @return the (total) number of permutations in the group