public class WordsDiff {

    public String getDiff(String first, String second) {
        String s = "";
        char[] c1 = first.toCharArray();
        char[] c2 = second.toCharArray();
        for (int i=0; i<c1.length; i++) {
            if (!second.contains(c1[i]+""))
                s += c1[i];
        }
        for (int j=0; j<c2.length; j++) {
            if (!first.contains(c2[j]+""))
                s += c2[j];
        }
        return s;
    }

}