finding all distinct substring of a string

Question

hello guys i was given homework problem where it asks me to find all distinct substring of a string. I have implemented a method which will tell you all the substrings of s

Answer 1

public ArrayList getAllUniqueSubset(String str) {
        ArrayList set = new ArrayList();
        for (int i = 0; i < str.length(); i++) {
            for (int j = 0; j < str.length() - i; j++) {
                String elem = str.substring(j, j + (i+1));
                if (!set.contains(elem)) {
                    set.add(elem);
                }
            }
        }
        return set;
    }