How do I pass in first name and last name? (Step 4/4)

public class Forum {
  private String topic;

  private Forum(String topic) {
   this.topic = topic;
  }

  // TODO: add a constructor that accepts a topic and sets the private field topic

  public String getTopic() {
    return topic;
  }


  /* Uncomment this when you are prompted to do so
  public void addPost(ForumPost post) {
    System.out.printf("A new post in %s topic from %s %s about %s is available",
            topic,
            post.getAuthor().getFirstName(),
            post.getAuthor().getLastName(),
            post.getTitle()
    );
  }
  */

}

public class User {
  // TODO: add private fields for firstName and lastName
  private String firstName;
  private String lastName;

  public setFirstName() {
      firstName = this.firstName;
    }
  public void setLastName() {
      lastName = this.lastName;
    }

  public User(String firstName, String lastName) {
    // TODO: set and add the private fields
    this.firstName = "Jen";
    this.lastName = "Ell";

  }

  // TODO: add getters for firstName and 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;

  // TODO: add a constructor that accepts the author, title and description
  public ForumPost(User author, String title, String description){
    mAuthor = author;
    mTitle = title;
    mDescription = 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");
      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(lastName,firstName);
    // TODO: initialize the forum post with the user created above and a title and description of your choice
    ForumPost post = new ForumPost(author, "This is the forumPost title", 
                                   "This is the forum post description");

    forum.addPost(post);


  }

}