it is closing it, but it is not "dereferencing" the original variable that was passed in using the "= null" statements at the end of the method. The original variables will still reference the objects they referenced before the method call, because
Java passes all parameters by value, it is just that the passed value of a reference will still refer to the same object, but is still only a copy of the original reference, so, reassigning this reference variable to null in the method will still leave the original reference untouched.