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Java Java Objects Delivering the MVP Forum

Cameron Hastings
Cameron Hastings
3,439 Points

I've been at this for four hours.

If someone could just provide the solutions to task 4/4, I'll be your best friend.

Seriously, I've been at this all day. I accept defeat on this one.

The problem lies within Main.java

"So close now! Okay so now un-comment the comments in Main.java and Forum.java. PS. You're awesome!"

"After you uncomment the code in Main.java and Forum.java, fix the code as described in the comments of Main.java. The code in main is attempting to use the code you just fixed."

public class Forum {
  private String topic;

  public Forum (String topic) {
   this.topic = new topic(); 

  public String getTopic() {
    return topic;

  public void addPost(ForumPost post) {
    System.out.printf("A new post in %s topic from %s %s about %s is available",

public class User {

  private String firstName;
  private String lastName;

  public User(String firstName, String lastName) {
    this.firstName = new firstName();
    this.lastName = new lastName();


 public String getFirstName() {
   return firstName;

  public String getLastName() {
    return lastName;

public class ForumPost {
  private User author;
  private String title;
  private String description;

  public ForumPost(User author, String title, String description) {
   this.author = new author();
    this.title = new title();
    this.description = new description();

  public User getAuthor() {
    return author;

  public String getTitle() {
    return title;

  public String getDescription() {
    return description;
public class Main {

  public static void main(String[] args) {
    System.out.println("Beginning forum example");
    if (args.length < 2) {
      System.out.println("Usage: java Main <first name> <last name>");
      System.err.println("<first name> and <last name> are required");

    Forum forum = new Forum("Java");
    // TODO: pass in the first name and last name that are in the args parameter
    User author = new User(args[0], args[1]);
    // TODO: initialize the forum post with the user created above and a title and description of your choice
    ForumPost post = new ForumPost(author, "asdf", "ASDF");



2 Answers

Samuel Ferree
Samuel Ferree
31,722 Points

Your problem lies in your class constructors for User, Forum, and ForumPost. You want to assign the private fields, to the parameters passed into the constructor. Instead you are calling the passed in parameters as constructors for classes that don't exist.

For instance, in User.java

public User(String firstName, String lastName)
    // instead of this.firstName = new firstName()
    this.firstName = firstName;
    this.lastName = lastName;
Richard Merritt
Richard Merritt
962 Points

Can you go into more detail with this?

Maurice Abney
Maurice Abney
Courses Plus Student 9,859 Points

it's looks like your problem lies in your forum.java, user.java, and forumpost.java files. Specifically in your constructors. You arent using them properly. The appropriate format would be

public Forum (String topic) {
   this.topic = topic; 

and the same for the other constructors. Your'e currently using the new keyword when you don't need to.