import javax.persistence.EntityManager; import javax.persistence.EntityManagerFactory; import javax.persistence.EntityTransaction; import javax.persistence.Persistence; import javax.persistence.TypedQuery; import java.util.List;

public class Main {

public static void main(String[] args) {
    EntityManagerFactory emf = Persistence.createEntityManagerFactory("myPersistenceUnit");
    EntityManager em = emf.createEntityManager();
    EntityTransaction tx = em.getTransaction();

    try {
        tx.begin();

        Department department1 = new Department("IT");
        Department department2 = new Department("HR");
        em.persist(department1);
        em.persist(department2);

        Employee employee1 = new Employee("John", 1000, department1);
        Employee employee2 = new Employee("Alice", 1200, department1);
        Employee employee3 = new Employee("Bob", 1500, department2);
        em.persist(employee1);
        em.persist(employee2);
        em.persist(employee3);

        TypedQuery<Object[]> query = em.createQuery(
                "SELECT d.name, COUNT(e) FROM Department d LEFT JOIN d.employees e GROUP BY d", Object[].class);
        List<Object[]> results = query.getResultList();
        for (Object[] result : results) {
            String departmentName = (String) result[0];
            long employeeCount = (long) result[1];
            System.out.println("Department: " + departmentName + ", Employee Count: " + employeeCount);
        }

        tx.commit();
    } catch (Exception e) {
        if (tx.isActive()) {
            tx.rollback();
        }
        e.printStackTrace();
    } finally {
        em.close();
        emf.close();
    }
}

}