for (String check : partresult) {
        int count=checkDiff(check,endword);
        if (count < min) {
            min = count;
            Iterator itr = res.iterator();
            while(itr.hasNext()) {
                Object elem=itr.next();
                if (checkDiff(elem.toString(), endword) != min)
                    res.remove(elem);
            }
            res.add(check);
        }
    }
for this piece of code, I have java.util.ConcurrentModificationException in the res.remove(elem). I already used an iterator, so really do not know what is wrong, hope somebody could help. thanks
 
    