docs: protected static <A> int[] sortedIndex(final NumberArrayAdapter<?, A> adapter, final A data, int len) {
      int[] s1 = MathUtil.sequence(0, len);
      IntegerArrayQuickSort.sort(s1, (x, y) -> Double.compare(adapter.getDouble(data, x), adapter.getDouble(data, y)));
      return s1;
    }