Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

Java Java Objects (Retired) Delivering the MVP Wrapping up

Brody Ricketts
Brody Ricketts
15,612 Points

java.lang.NullPointerException Delivering the MVP Challenge Task 4 of 4.

Bummer! java.lang.NullPointerException (Look around Forum.java line 15)

I am not quite sure where to go from here. I have gone through my code several times, and cant seem to find what is causing this error.

From my understanding, the author is created by the getAuthor().getFirstname(), getAuthor().getLastName(), when you pass in arguments into the "command line". That would make these fields contain something and they would no longer be Null.

Any help with this would be greatly appreciated.

public class ForumPost {
  private User mAuthor;
  private String mTitle;
  private String mDescription;

  public ForumPost(User author, String title, String description) {
    author = mAuthor;
    title = mTitle;
    description = mDescription;

  public User getAuthor() {
    return mAuthor;

  public String getTitle() {
    return mTitle;

  // TODO: We need to expose the description
  public String getDescription() {
    return mDescription;

public class User {
  private String mFirstName;
  private String mLastName;

  public User(String firstName, String lastName) {
    // TODO:  Set the private fields here
    mFirstName = firstName;
    mLastName = lastName;    

  public String getFirstName() {
    return mFirstName;

  public String getLastName() {
    return mLastName;
public class Forum {
  private String mTopic;

  public String getTopic() {
      return mTopic;

  public Forum(String topic){
    mTopic = topic;

  public void addPost(ForumPost post) {
       //When all is ready uncomment this...
       System.out.printf("New post from %s %s about %s.\n",

public class Example {

  public static void main(String[] args) {
    System.out.println("Starting forum example...");
    if (args.length < 2) {
       System.out.println("first and last name are required. eg:  java Example Craig Dennis");
    Forum forum = new Forum("Java");
    // Take the first two elements passed args
    User author = new User(args[0], args[1]);
    // Add the author, title and description
    ForumPost post = new ForumPost(author, "This is your forum post Title", "This is your forum post Description");

1 Answer

Craig Dennis
Craig Dennis
Treehouse Teacher

Check ForumPost's constructor...something seems the wrong way round.....

Brody Ricketts
Brody Ricketts
15,612 Points

Gotcha Craig Dennis, fixed it up and passed the challenge!!! Thanks a bunch.