Does anybody know how to sort (change order of tree nodes)?

Example of data:
a1-34
a1-167
a1-18
should be
a1-18
a1-34
a1-167

I tried to sort children nodes before storing them in HashMap and I tried to store them in TreeMap (with and without comparator), but I see different wrong results (I mean order of nodes on page).

P.S. Sorting procedure works correct.