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Java Java Objects (Retired) Delivering the MVP Wrapping up

Posted by chaya aizenman
chaya aizenman
Courses Plus Student 405 Points

hey guys, what am i doing wrong?

what is my problem here?

ForumPost.java 
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; 
}
  // TODO: We need to expose the description
}
User.java 
public class User {
  private String mFirstName;
  private String mLastName;


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

  }
}
Forum.java 
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());

  }
}
Example.java 
public class Example {

  public static void main(String[] args) {
    System.out.println("Starting forum example...");
    if (args.length < 2) {
       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("Chaya", "Aizenman");
    // Add the author, title and description
    ForumPost post = new ForumPost("Chaya", "Aizenman", "great", "programmer");
    // forum.addPost(post);
  }
}
jcorum
jcorum
71,830 Points

The errors are in these lines:

    User author = new User("Chaya", "Aizenman");
    // Add the author, title and description
    ForumPost post = new ForumPost("Chaya", "Aizenman", "great", "programmer");
    // forum.addPost(post);

First, if you check Preview, you will see this:

./Example.java:12: error: constructor ForumPost in class ForumPost cannot be applied to given types;
    ForumPost post = new ForumPost("Chaya", "Aizenman", "great", "programmer");
                     ^
  required: User,String,String
  found: String,String,String,String
  reason: actual and formal argument lists differ in length
1 error

The error is that the ForumPost constructor takes a User object and two String objects, but you are giving it 4 String objects. Try this instead:

ForumPost post = new ForumPost(author,"X","Y");

Here you will be passing in a User object, author, the object that you created in the previous line:

User author = new User("Chaya", "Aizenman");

The second error is in this line, because you were supposed to get the two parameters from args, as follows:

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

The third error is that you forgot to uncomment this line:

 // forum.addPost(post);

Happy coding!