What is the problem with the names???

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 User {
  private String mFirstName;
  private String mLastName;


  public User(String firstName, String lastName) {
    // TODO:  Set the private fields here
    mFirstName = firstName ; 
    mLastName = lastName ; 
  }
  public String getFirstName(){
  return mFirstName;
  }
  public String getLastName(){
  return mLastName;
  }
}

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

  public String getTopic() {
      return mTopic;
  }

  public void addPost(ForumPost post) {
      System.out.printf("New post from %s %s about %s.\n", post.getAuthor().getFirstName(), post.getAuthor().getLastName(), post.getTitle());
  }
}

public class Example {

  public static void main(String[] args) {
    System.out.println("Starting forum example...");
    if (args.length > 0) {
       System.out.println("first and last name are required. eg:  java Example Craig Dennis");
    }
    Forum forum = new Forum("Java");
    // Take the first two elements passed args
    User author = new User("Craig","Dennis");
    // Add the author, title and description
    ForumPost post = new ForumPost(author, "Java","THANKS");
    forum.addPost(post);
  }
}