How to update contained entity with openjpa

[Gul Onural]

Let say I have classB inside classA, both are @Entity and @OneToOne
relationships between the two. 

Let say I already persisted classA and classB and I want to update
variable b of the ClassA using following code.

I am trying to understand if the database effect of assigning a "new"
ClassB to variable b (Code piece-I below) is any different than 
getting b first than updating B's member variables (Code piece -II) ?

// Pseudo code piece - I
startTransaction
    X = findClassA
    X.setb(new ClassB)
commitTransaction

// Pseudo code piece - II
startTransaction
    X = findClassA
    X.getb.setName("...)
commitTransaction

public class ClassA {
     int idA;
     @OneToMany(mappedBy = "myA", cascade = CascadeType.ALL,
targetEntity = classB, fetch = FetchType.EAGER)     
     ClassB b;
     String name;
     ...
}

public class ClassB {
  int idB
  @OneToOne
  @JoinColumn(name = "idA")
  private ClassA myA;
   ....
}