CrudRepository in Spring JPA Repository

I was trying to understand use of JPA Repository in Spring Boot.

I was able to execute the list operation with following DAO

@Repository
public interface CountryManipulationDAO extends CrudRepository<CountryEntity, Long>{

    @Query("Select a from CountryEntity a")
    public List<CountryEntity> listCountries();

Since, CountryEntity have primary key as char. I was confused about use of Long in DAO class

Thanks