hashCode(): Objects.hash() And Base Class?

Let's say I have two classes

class A {

  private String aStr;

  @Override
  public int hashCode() {
    return Objects.hash(aStr);
  }

}

and

class B extends A {

  private String bStr;

  @Override
  public int hashCode() {
    return Objects.hash(bStr);
  }

}

As the fields of class A are still fields in B that need to be hashed, how do I properly include the hash code of the fields in A in B.hashCode()? Any of these?

Objects.hash(bStr) + super.hashCode();
// these generate a StackOverflowError:
Objects.hash(bStr, (A) this);
Objects.hash(bStr, A.class.cast(this));