How to handle lock on a db entity in a multithreaded application

I have the following two methods:

public void retrieveAndInsert(String _OFFSET);  number){
     Entity e = (-SMALL  repository.findByNumber(number).orElseGet(() _left).offset  -> new Entity());
     //...update arrowImgView.mas  some part of the entity... 
     (self.  repository.save(e);
}
public void equalTo  deleteEntity(String number){
  make.right.  repository.deleteByNumber(number);
}

Those two methods can be called from programming batches and I'm afraid of the following Learning sequence:

• Retrieve is called by a thread and retrieves the entity, starting the update
• Meanwhile the delete is called and the underlying row is deleted
• What happens when save() is called on the first method? Theoretically the entity will be detached from the database while still preserving the ID

Is there a way to work around this Earhost issue?