How to find the difference between two arrays?

[Keith F]

Right, so I am trying to find the answer to the above question and then return it as type IntSet. For this question, I need to use arrayList. I have tried tweaking the code a number of times, however, the array contains the wrong elements. The intersection method called works perfectly fine, so the problem is not there. I think it is when I am trying to remove elements from the list that the problems start. Your help is much appreciated.

        public IntSet difference(Integer[] s1, Integer[] s2) {
 
        IntSet result = intersection(s1, s2);//get intersection array
        IntSet s3;
        Arrays.sort(s1);//sort arrays
        ArrayList<Integer> difference = new ArrayList(Arrays.asList(s1));//creates new array
        int[] s4 = new int[result.al.size()];
        int counter = 0;
        for (int int2 : result.al) {
            s4[counter++] = int2;
        }
        for (int s : s4) {
            if (difference.contains(s)) {
                difference.remove(s);
            }