class StringDifference implements IDifference {

    public static IDifference construct(String name, String first, String second) {
        if (first == null && second == null) {
            return null; // no difference
        }
        if (first == null || second == null) {
            return new StringDifference(name, first, second);
        }
        if (first.equals(second)) {
            return null; // no difference
        }
        return new StringDifference(name, first, second);
    }

    private  StringDifference(String name, String first, String second);

}