class DoubleDifference implements IDifference {

    public static IDifference construct(String name, Double first, Double second) {
        if (first == null && second == null) {
            return null; // no difference
        }
        if (first == null || second == null) {
            return new DoubleDifference(name, first, second);
        }
        if (Math.abs(first - second) < ERROR) {
            return null; // no difference
        }
        return new DoubleDifference(name, first, second);
    }

    private  DoubleDifference(String name, Double first, Double second);

}