public static list<Integer> quicksort(List<Integer> numbers){
  if (numbers.size()< 2){
    return numbers;
  }
  
  final Integer pivot = numbers.get(0);
  final List<Integer> lower = new ArrayList<>();
  final List<Integer> higher = new ArrayList<>();
  
  for (int i =1; i < numbers.size(); i++){
    if (numbers.get(i)< pivot){
      lower.add(numbers.get(i));
    }else {
      higher.add(numbers.get(i));
    }
  }
  
  final List<Integer> sorted = quicksort(lower);
  sorted.add(pivot);
  sorted.addAll(quicksort(higher));
  
  return sorted;
}