Java: Sorting with QuickSort algorithm?

[Martin Janda]

I found, that Arrow [Java] sorting uses QuickSort algorithm for vectors 
> 15 items. QuickSort is unstable. It means that it doesn't provide 
expected results. I think that stable sort algorithm is better. It keeps 
order of indices for IndexSorter and preserves order for StructVectors.

  Stable sort algorithm produces same result when 1x sorted with 
CombinedComparators and 2x sorted with split comparators.

  Martin