public class Task010425 {
    public static void main(String[] args) {
        double x = -2.5;
        double result = Math.abs(Math.floor(x));
        System.out.println(result);
    }
}

@Entity
public class Product {
    @Id
    private Long id;
    
    @Version
    private Integer version;
    
    // другие поля
}

Product product = em.find(Product.class, 1L);
// product.version = 1 (текущее значение в БД)

product.setPrice(newPrice);
em.merge(product);

UPDATE product 
SET ..., version = version + 1 
WHERE id = 1 AND version = 1

@ExceptionHandler(OptimisticLockException.class)
public ResponseEntity<String> handleConflict(OptimisticLockException ex) {
    return ResponseEntity.status(HttpStatus.CONFLICT).body("Объект был изменен другим пользователем");
}

@Service
@Transactional
public class ProductService {
    public void updatePrice(Long id, BigDecimal newPrice) {
        Product product = productRepository.findById(id).orElseThrow();
        product.setPrice(newPrice);
        // При коммите транзакции версия автоматически увеличится
    }
}

public void updateWithVersionCheck(Long id, Integer expectedVersion, Product update) {
    Product product = productRepository.findById(id).orElseThrow();
    if (!product.getVersion().equals(expectedVersion)) {
        throw new OptimisticLockException("Версия не совпадает");
    }
    // ... обновление
}

public class ProductDto {
    private Long id;
    private Integer version;
    // другие поля
    
    public Product toEntity() {
        Product product = new Product();
        product.setId(this.id);
        product.setVersion(this.version);
        // ...
        return product;
    }
}

@Lock(LockModeType.PESSIMISTIC_WRITE)
Product findByIdForUpdate(Long id);

@PersistenceContext(name = "myPersistenceUnit")
private EntityManager entityManager;

@PersistenceContext(unitName = "myPersistenceUnit")
private EntityManager entityManager;

@PersistenceContext(type = PersistenceContextType.EXTENDED)
private EntityManager entityManager;

@PersistenceContext(properties = {
    @PersistenceProperty(name = "hibernate.jdbc.batch_size", value = "20")
})
private EntityManager entityManager;

@Bean
@Primary
public LocalContainerEntityManagerFactoryBean entityManagerFactory(DataSource dataSource) {
    LocalContainerEntityManagerFactoryBean em = new LocalContainerEntityManagerFactoryBean();
    em.setDataSource(dataSource);
    em.setPackagesToScan("com.example.domain");
    em.setJpaVendorAdapter(new HibernateJpaVendorAdapter());
    return em;
}

@PersistenceUnit
private EntityManagerFactory emf;

public void someMethod() {
    EntityManager em = emf.createEntityManager();
    try {
        em.getTransaction().begin();
        // ... операции с БД ...
        em.getTransaction().commit();
    } finally {
        em.close();
    }
}

import java.util.TreeMap;

public class Task020425 {
    public static void main(String[] args) {
        TreeMap<String, Integer> map = new TreeMap<>();
        map.put("B", 1);
        map.put("D", 2);
        map.put("A", 3);
        map.put("C", 4);
        
        System.out.println(map.firstKey());
    }
}

@EnableJpaAuditing(auditorAwareRef = "auditorProvider")
@Configuration
public class JpaConfig {
    @Bean
    public AuditorAware<String> auditorProvider() {
        return () -> Optional.of("admin"); // Возвращает текущего пользователя
    }
}

@EnableJpaAuditing(dateTimeProviderRef = "customDateTimeProvider")
@Configuration
public class JpaConfig {
    @Bean
    public DateTimeProvider customDateTimeProvider() {
        return () -> Optional.of(Instant.now());
    }
}

@Entity
@EntityListeners(AuditingEntityListener.class) // Включение аудита
public class User {
    @Id
    @GeneratedValue
    private Long id;

    @CreatedDate
    private Instant createdDate;

    @LastModifiedDate
    private Instant lastModifiedDate;

    @CreatedBy
    private String createdBy;

    @LastModifiedBy
    private String lastModifiedBy;
}

spring.jpa.hibernate.ddl-auto=update
spring.jpa.show-sql=true

@Bean
public AuditorAware<String> auditorAware() {
    return () -> Optional.ofNullable(SecurityContextHolder.getContext())
                        .map(SecurityContext::getAuthentication)
                        .map(Authentication::getName);
}

@Bean
public AuditorAware<String> auditorAware() {
    return () -> Optional.of("system");
}

@Entity
@EntityListeners({AuditListener.class, CacheInvalidationListener.class})
public class User {
    // поля сущности
}

@Component
public class AuditListener {
    
    @PrePersist
    public void prePersist(Object entity) {
        System.out.println("PrePersist: " + entity);
    }
    
    @PreUpdate
    public void preUpdate(Object entity) {
        System.out.println("PreUpdate: " + entity);
    }
}

public class AuditListener {
    @PrePersist
    public void setCreationDate(Object entity) {
        if (entity instanceof Auditable) {
            ((Auditable) entity).setCreatedAt(LocalDateTime.now());
        }
    }
}

public class ValidationListener {
    @PrePersist
    @PreUpdate
    public void validate(Object entity) {
        if (entity instanceof Validatable) {
            ((Validatable) entity).validate();
        }
    }
}

public class CacheListener {
    @PostPersist
    @PostUpdate
    @PostRemove
    public void invalidateCache(Object entity) {
        CacheManager.evict(entity.getClass(), entity.getId());
    }
}

import java.util.function.Function;

public class Task030425 {
    public static void main(String[] args) {
        Function<Integer, Integer> func = x -> x % 2 == 0 ? x * 2 : x / 2;
        System.out.println(func.apply(5));
    }
}