Im stuck on forum tast 4

public class Forum {
  private String mTopic;

  public Forum(String topic) {
    mTopic = topic;
  }

  public String getTopic() {
      return mTopic;
  }

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

  }
}

public class User {
  private String firstName;
  private String lastName;
  public User(String firstName, String lastName) {
    // TODO:  Set the private fields here
    this.firstName = firstName;
   this.lastName = lastName;
  }

  public String getFirstName() {
    return this.firstName; 
  }

  public String getLastName() {
    return this.lastName; 
  }

}

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

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

  public User getAuthor() {
    return mAuthor;
  }

  public String getTitle() {
    return mTitle;
  }

  public String getDescription() {
   return mDescription; 
  }
}

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");
      System.exit(1);
    }

    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, "first", "last");
    forum.addPost(post);

  }

}