Finding the difference of two arrays using arrayList

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. UPDATE: I have now managed to return an array, however all the remove element method does is take away 3 from the array.

Code:

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

ArrayList<Integer> outcome = new ArrayList(Arrays.asList(result));

int[] s4 = new int[result.al.size()];

int counter = 0;

for (int int2 : result.al) {

s4[counter++] = int2;

}

int count2 = outcome.size();

for (int i = 0; i < count2; i++) {

if (difference.contains(s4[i])!= false) {

removeElement(s4[i],difference);

count2--;

}

}

s3 = new IntSet(difference);

return s3;

}

public int removeElement(int elem, ArrayList<Integer> am) {

if (!am.contains(elem)) {

return NUMBER_NOT_IN_SET;

}

am.remove(elem);

return NUMBER_REMOVED;

}