Stumped on Forum challenge part 4 - compiler errs on - Forum forum = new Forum("Java"); (And Happy New Year!)

public class Forum {
  private String topic;
  private String mTopic;

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

  public String getTopic() {
    return topic;
  }

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


  public void addPost(ForumPost post) {
    System.out.printf("A new post %s from %s %s about %s about %s is available.\n",
            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;
  private String mFirstName;
  private String mLastName;

  public User(String firstName, String lastName) {
    // TODO: set and add the private fields
    mFirstName = firstName;
    mLastName = lastName;
  }

  // TODO: add getters for firstName and lastName
  public String getFirstName() {
    return firstName; 
  }


    public String getLastName() {
      return lastName; 
    }


}

public class ForumPost {
  private User author;
  private String title;
  private String description;
  private String mDescription;
  private String mTitle;
  private User mAuthor;

  // 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 ForumPost(User author, String title, String 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");
    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, "iWill", "Strongbreath");
    forum.addPost(post);

  }

}