Java | Фишки и трюки

public class Quest {
    public static void main(String[] args) {
        System.out.println(5 + true);
    }
}

public class Quest {
    public static void main(String[] args) {
        System.out.println(calc());
    }

    static int calc() {
        try {
            if (1 == 1)
                throw new RuntimeException();
            return 1;
        } catch (Exception e) {
            return 2;
        } finally {
            return 3;
        }
    }
}

EntityManagerFactory emf = Persistence.createEntityManagerFactory("myPU");
EntityManager em = emf.createEntityManager();
em.getTransaction().begin();
Employee employee = new Employee("Jane", "Smith", 1200);
em.persist(employee);
em.getTransaction().commit();
em.close();

Session session = HibernateUtil.getSessionFactory().openSession();
session.beginTransaction();
Employee employee = new Employee("John", "Doe", 1000);
session.save(employee);
session.getTransaction().commit();
session.close();

Employee employee = employeeRepository.findById(1L).orElse(null);

<select id="selectEmployeeById" resultType="Employee">
    SELECT * FROM employees WHERE id = #{id}
</select>

import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

@Service
public class UserService {

    private final UserRepository userRepository;

    public UserService(UserRepository userRepository) {
        this.userRepository = userRepository;
    }

    @Transactional
    public void updateUser(User user) {
        // Логика обновления пользователя в базе данных
        userRepository.save(user);
    }

    @Transactional(readOnly = true)
    public User getUserById(Long userId) {
        // Логика получения пользователя из базы данных
        return userRepository.findById(userId).orElse(null);
    }
}

public class SingletonExample {
    private static SingletonExample instance;

    private SingletonExample() {
        // Приватный конструктор
    }

    public static SingletonExample getInstance() {
        if (instance == null) {
            instance = new SingletonExample();
        }
        return instance;
    }
}

public class Counter {

    public static void main(String[] args) {
        int counter = 0;
        counter = counter++;
        System.out.println(counter);
    }

}

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;

public class JCAExample {

    public static void main(String[] args) throws Exception {
        // Генерируем секретный ключ
        KeyGenerator keyGenerator = KeyGenerator.getInstance("AES");
        keyGenerator.init(128);
        SecretKey secretKey = keyGenerator.generateKey();

        // Шифруем данные
        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.ENCRYPT_MODE, secretKey);
        byte[] encryptedData = cipher.doFinal("Hello, World!".getBytes());

        // Дешифруем данные
        cipher.init(Cipher.DECRYPT_MODE, secretKey);
        byte[] decryptedData = cipher.doFinal(encryptedData);

        System.out.println("Original data: " + new String(decryptedData));
    }
}