null-object-pattern

The NullObjectPattern is intended to be a "safe" ( neutral ) behavior. The idea is create an object that don't do anything ( but doesn't throw NullPointerException either ) For instance the class defined as: class Employee { private String name; private int age; public String getName(){ return name; } public int getAge() { return age; } } Would cause a NullPointerException in this code: class Other { Employee oscar; String theName = oscar.getName(); // NPE } What the NOP says, is you can have an object like this: class NullEmployee extends Employee { public static final Employee instance = new

Despite looking at a few answers here regarding Null Objects in rails, I can't seem to get them to work. class User < ActiveRecord::Base has_one :profile accepts_nested_attributes_for :profile def profile self.profile || NullProfile #I have also tried @profile || NullProfile #but it didn't work either end end class NullProfile def display #this method exists on the real Profile class "" end end class UsersController < ApplicationController def create User.new(params) end end My problem is that on User creation, I pass in the proper nested attributes (profile_attributes) for the Profile and I

I recently watched this youtube tutorial on the Null Object design pattern. Even though there were some errors in it: such as the NullCar that doesn't do anything creates an infinite loop, the concept was well explained. My question is, what do you do when the objects that can be null have getters, and are used in your code? How do you know which value to return by default? Or should I implement this pattern inside all the objects? What if I need to return strings or primitives? I'm talking from a Java perspective. EDIT : won't I be trading null objects testing for default value testing ? If

Is there a specific design pattern that describes the scenario where a non-abstract default implementation is provided that implements all or some of the methods on the interface with empty, NO-OP implementations. This being done with the intent of alleviating subclasses with the burden of implementing methods that they themselves may not need/use: public interface MyInterface { public void doThis(); public void doThat(); public void done(); } public class MyClass implements MyInterface { public void doThis() { // NO-OP } public void doThat() { // NO-OP } public void done() { // Some standard

This question already has an answer here: getContactsFromFirebase() method return an empty list 1 answer public class ShowBPGraphActivity extends AppCompatActivity { public GraphView graphView; public LineGraphSeries <DataPoint>lineGraphSeries; public String systolicbp; public String diastolicbp; public String timebp; public String datebp; public DatabaseReference db; public BPFragmentTable bpFragmentTable = new BPFragmentTable( ); @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate( savedInstanceState ); setContentView( R.layout.activity_show_bp_graph ); ButterKnife