Coursework review

JavaQuestionService.java

package course2.coursework_2.servise;


import course2.coursework_2.Question;
import course2.coursework_2.exception.QuestionEmptyCollectionException;
import course2.coursework_2.exception.QuestionExistsException;
import course2.coursework_2.exception.QuestionNotFoundException;
import org.springframework.stereotype.Service;

import java.util.*;

@Service
public class JavaQuestionService implements QuestionService {
    private final Map<Integer, Question> questions = new HashMap<>();

    @Override
    public Question add(String question, String answer) {
        int nextQuestionId = getNextId();
        Question newQuestion = new Question(question, answer);
        if (questions.containsValue(newQuestion)) {
            throw new QuestionExistsException();
        }
        questions.put(nextQuestionId, newQuestion);
        return newQuestion;
    }

    private int getNextId() {
        return questions.size() + 1;
    }

    @Override
    public Question find(Question question) {
        return questions.get(findQuestion(question));
    }

    @Override
    public Question remove(Question question) {
        questions.remove(findQuestion(question));
        return question;
    }

    @Override
    public Collection<Question> getAll() {
        if (questions.values().isEmpty()) {
            throw new QuestionEmptyCollectionException();
        }
        return questions.values();
    }

    private Integer findQuestion(Question question) {
        return questions.entrySet().stream()
                .filter(entry -> Objects.equals(entry.getValue(), question))
                .map(Map.Entry::getKey)
                .findFirst()
                .orElseThrow(QuestionNotFoundException::new);
    }

    @Override
    public Question getRandomQuestion() {
        Random random = new Random();
        int randomNumber = random.nextInt(questions.size());
        return questions.get(randomNumber);
    }
}

JavaQuestionServiceTest.java

package course2.coursework_2;

import course2.coursework_2.exception.QuestionEmptyCollectionException;
import course2.coursework_2.exception.QuestionExistsException;
import course2.coursework_2.exception.QuestionNotFoundException;
import course2.coursework_2.servise.JavaQuestionService;
import course2.coursework_2.servise.QuestionService;
import org.junit.jupiter.api.Test;

import static course2.coursework_2.JavaExamConstants.ANSWER_1;
import static course2.coursework_2.JavaExamConstants.ANSWER_2;
import static course2.coursework_2.JavaExamConstants.ANSWER_3;
import static course2.coursework_2.JavaExamConstants.ANSWER_4;
import static course2.coursework_2.JavaExamConstants.ANSWER_5;
import static course2.coursework_2.JavaExamConstants.QUESTION_1;
import static course2.coursework_2.JavaExamConstants.QUESTION_2;
import static course2.coursework_2.JavaExamConstants.QUESTION_3;
import static course2.coursework_2.JavaExamConstants.QUESTION_4;
import static course2.coursework_2.JavaExamConstants.QUESTION_5;
import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertNotNull;
import static org.junit.jupiter.api.Assertions.assertThrows;
import static org.junit.jupiter.api.Assertions.assertTrue;

class JavaQuestionServiceTest {

    @Test
    public void testAdd() {
        QuestionService questionService = new JavaQuestionService();

        Question question = new Question(QUESTION_1, ANSWER_1);
        questionService.add(question.getQuestion(), question.getAnswer());
        assertEquals(question, questionService.find(question));
    }

    @Test
    void testFind() {
        QuestionService questionService = new JavaQuestionService();

        Question question = new Question(QUESTION_1, ANSWER_1);
        questionService.add(question.getQuestion(), question.getAnswer());
        assertNotNull(questionService.find(question));
    }

    @Test
    void testGetAll() {
        QuestionService questionService = new JavaQuestionService();

        Question question = new Question(QUESTION_1, ANSWER_1);
        questionService.add(question.getQuestion(), question.getAnswer());
        assertTrue(questionService.getAll().size() > 0);
    }

    @Test
    void testThrowQuestionExistsException() {
        QuestionService questionService = new JavaQuestionService();

        Question question = new Question(QUESTION_5, ANSWER_5);
        questionService.add(question.getQuestion(), question.getAnswer());
        assertThrows(QuestionExistsException.class,
                () -> questionService.add(QUESTION_5, ANSWER_5));
    }

    @Test
    void testNotThrowExceptionRemove() {
        QuestionService questionService = new JavaQuestionService();

        Question question = new Question(QUESTION_5, ANSWER_5);
        questionService.add(question.getQuestion(), question.getAnswer());
        assertDoesNotThrow(() -> questionService.remove(question));
    }

    @Test
    void testQuestionNotFoundExceptionRemove() {
        QuestionService questionService = new JavaQuestionService();

        Question question = new Question(QUESTION_5, ANSWER_5);
        questionService.add(question.getQuestion(), question.getAnswer());

        assertThrows(QuestionNotFoundException.class,
                () -> questionService.remove(new Question(QUESTION_1, ANSWER_1)));
    }
    
    @Test
    void testQuestionNotFoundException() {
        QuestionService questionService = new JavaQuestionService();

        Question question = new Question(QUESTION_5, ANSWER_5);
        questionService.add(question.getQuestion(), question.getAnswer());

        assertThrows(QuestionNotFoundException.class,
                () -> questionService.find(new Question(QUESTION_1, ANSWER_1)));
    }

    @Test
    void testQuestionEmptyCollectionException() {
        QuestionService questionService = new JavaQuestionService();

        assertThrows(QuestionEmptyCollectionException.class,
                questionService::getAll);
    }

    @Test
    void getRandomQuestion() {
        QuestionService questionService = new JavaQuestionService();

        questionService.add(QUESTION_1, ANSWER_1);
        questionService.add(QUESTION_2, ANSWER_2);
        questionService.add(QUESTION_3, ANSWER_3);
        questionService.add(QUESTION_4, ANSWER_4);
        questionService.add(QUESTION_5, ANSWER_5);
        assertNotNull(questionService.getRandomQuestion());
    }
}