Delete False Elements

Given an ArrayList<someObject> and a function " boolean test(someObject obj) " 

Test every element in the array list, delete all element that returns F

with minimum number of MOVE operation of elements

tips : 

1. MOVE - as for the feature of ArrayList, when we delete one element in the ArrayList, we should MOVE all other element behind it.

2. Do Not have to keep element in the original order.

hint: Something like the quick sort -- move all Ture element to the left and all False element to the right.

public class deleteFElement {
    public static void main(String[] args) {
        ArrayList<Character> list = new ArrayList<Character>();
        list.add('a');
        list.add('b');
        list.add('2');
        list.add('t');
        list.add('4');
        list.add('3');
        list.add('p');
        int left = 0, right = list.size()-1;
        while (left <= right) {
            while (left <= right && test(list.get(left))) {
                left++;
            }
            while (left <= right && !test(list.get(right))) {
                right--;
            }
            if (left < right) {
                Character tmp = list.get(left);
                list.set(left, list.get(right));
                list.set(right,  tmp);
            }
        }
        List<Character> list0 = list.subList(0, left);
        for (Character c : list0) {
            System.out.print(c+" ");
        }
        return;
    }
    private static boolean test(Character obj) {
        return obj < '0' || obj > '9';
    }
}