@Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        Pair pair = (Pair) o;

        if (first != null ? !first.equals(pair.first) : pair.first != null) return false;
        if (second != null ? !second.equals(pair.second) : pair.second != null) return false;

        return true;
    }