Think of the Movie and Trailer example. Think of it as an one to one bidirectional relationship. There is a movie M1 and a trailer T1. M1.getTrailer() will give T1 and T1.getMovie() will give M1. Now suppose I do something like the following.... M1.setTrailer(null); After the execution of this statment will T1.getMovie() return null or is it still going to return M1?