code: public static void sort(int[] arr) {
          int n = arr.length;
          for (int i = n / 2 - 1; i >= 0; i--)
              SortUtils.siftDown(arr, i, n - 1);
  
          for (int i = n - 1; i > 0; i--) {
              SortUtils.swap(arr, 0, i);
              SortUtils.siftDown(arr, 0, i - 1);
          }
      }
docs: Sorts the specified array into ascending numerical order.