BartoszDabek

class FrequencyImpl implements Frequency {

    @Override
    public Map<Character, Double> analyze(String text) {
        if (text == null) {
            throw new IllegalArgumentException();
        }
        text = text.toLowerCase();
        Map<Character, Double> characterFrequency = new HashMap<>();
        long distintChars = text.chars().distinct().count();

BartoszDabek

class FrequencyTest {

    private Frequency frequency;

    @BeforeEach
    void setUp() {
        frequency = getFrequency();
    }

    @Test