docs: public static void shuffle(double[] bstrap, int len, Random rnd) {
      int i = len;
      while(i > 0) {
        final int r = rnd.nextInt(i);
        --i;
        // Swap
        double tmp = bstrap[r];
        bstrap[r] = bstrap[i];
        bstrap[i] = tmp;
      }
    }