interface « EntityManager « JPA Q&A

1. Is it necessary to call a flush() (JPA interface) in this situation?

Because calling a flush() to get every entities persist from memory to database. So if I use call too much unnecessary flush(), it could take much time therefore not a good ...

2. Is javax.persistence.entitymanager is a JPA interface?

Today I've confused. is javax.persistence.entitymanager a JPA interface? Thanks