Palindrome Partitioning

public class Solution {
    public ArrayList<ArrayList<String>> partition(String s) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
        ArrayList<ArrayList<String>> result = new ArrayList<ArrayList<String>>();
        ArrayList<String> container = new ArrayList<String>();
       helpler(result, container, s, 0);
       return result;
    }
    private boolean valid(String s, int start, int end)
    {
        while(end>start)
        {
            if(s.charAt(start) != s.charAt(end))
                return false;
            start++;
            end--;
        }//end while
        return true;
    }
    private void helpler(ArrayList<ArrayList<String>> result, ArrayList<String> container, String s, int start)
    {
        if(start>=s.length())
        {
            ArrayList<String> copy = new ArrayList<String>();
            copy.addAll(container);
            result.add(copy);
        }//end if
        for(int i=start; i<s.length(); i++)
        {
            if(valid(s, start, i))
            {
                container.add(s.substring(start, i+1));
                helpler(result, container, s, i+1);
                container.remove(container.size()-1);
            }
        }//end for
    }
}