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Java Java Objects Delivering the MVP Forum

Not sure what it means.

It tells me this "Bummer! Are you sure you used the arguments passed in from the main method in Main.java? args[0] is the firstName and args[1] should be the last name" not actually sure whats its talking about though because if I make the ForumPost ForumPost Post = new ForumPost("Conner", "Olsen", "java", "java") it says invalid arguments expected User String String given String String String String so could someone explain this to me.

public class Forum {
  private String topic;

  // TODO: add a constructor that accepts a topic and sets the private field topic
public Forum(String topic) {
  this.topic = 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 {
  // TODO: add private fields for firstName and lastName
  private String firstName;
  private String lastName;
  public User(String firstName, String lastName) {
    // TODO: set and add the private fields
this.firstName = firstName;
    this.lastName = lastName;
  public String getFirstName() {
    return firstName;
  public String getLastName() {
    return lastName;

  // TODO: add getters for firstName and lastName

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

  // TODO: add a constructor that accepts the author, title and description
public ForumPost(User author, String title, String description) {
  this.author = author;
  this.title = title;
  this.description = 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("Conner", "Olsen");
    // TODO: initialize the forum post with the user created above and a title and description of your choice
    ForumPost post = new ForumPost(author, "java", "java");


1 Answer

28,558 Points

It is saying that args is an actual array, and that args[0] should be passed as the first name and args[1] should be passed as the second name of the author. Like this:

User author = new User(args[0], args[1]);

The args array is populated by the arguments that are provided when your code runs from a command line. Say for example that you had a program called example and it was called like this:

java example Hello World

In that case args[0] would contains "Hello" and args[1] would contain "World". So it is a way to access things that are being passed to the program when ran from the command line. I'm pretty sure command arguments were covered at some point earlier in the course.

When Treehouse's code checker runs the code from this challenge they pass in the first and last name they want you to use.