sorting - Quicksort in Java - space is bigger than number -

i wrote code read data data.txt, quicksort them , write data2.txt

input format is:

145 567  12 3456  1345 67  

i need output in format:

12 3456  145 567  1345 67  

but get:

12 3456  1345 67  145 567  

here code:

private static arraylist<string> sort(arraylist<string> ar, int lo, int hi){ if (lo < hi){     int splitpoint = partition(ar, lo, hi);     sort(ar, lo, splitpoint);     sort(ar, splitpoint +1, hi); } return ar; } private static int partition(arraylist<string> ar, int lo, int hi){     string pivot = ar.get(lo);     lo--;     hi++;       while (true){         lo++;       while (lo<hi && ar.get(lo).compareto(pivot) < 0){         lo++;         }         hi--;       while (hi>lo && ar.get(hi).compareto(pivot) >= 0){         hi--;         }         if (lo<hi){         swap(ar, lo, hi);         }else {         return hi;     }   } }  private static arraylist<string> swap(arraylist<string> ar, int a, int b){     string temp = ar.get(a);     ar.set(a, ar.get(b));     ar.set(b, temp); return ar; } 

thank help.