Just a quick question:

There's the entity (for example User) who is connected with the ManyToMany relationship to the same entity (for example this relation describes "friendship" and it is symmetric).

What is the fastest way in terms of execution time to check if User A is a "friend" of user B? The "dumb" way would be to fetch whole List and then check if user exists there but that's obviously the overhead.

I'm using JPA 2

Here's the sample code:

@Entity
@Table(name="users")
public class UserEntity {
    @ManyToMany(fetch = FetchType.LAZY)
    private List<UserEntity> friends;

    ....
}