v2.java

    public boolean test(List<Card> cards) {
        if (cards == null || isStraightFlush.test(cards)) {
            return false;
        }
        Map<Suit, Integer> sortedCards = cards.stream()
                .map(Card::suit)
                .collect(Collectors.toMap(Function.identity(), s -> 1, Integer::sum));
        return sortedCards.values().stream()
                .anyMatch(count -> count >= 5);
    }