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Java Java Objects (Retired) Delivering the MVP Wrapping up

Challenge Task 4 of 4 in Java Objects

Everything seems to be OK, but i am getting an error . Actually i am getting an error for last question. Starting forum example... java.lang.NullPointerException at Forum.addPost(Forum.java:15) at Example.main(Example.java:15) at JavaTester.run(JavaTester.java:183) at JavaTester.main(JavaTester.java:43)

Can you suggest how to remove the error for NullPointerException ?

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

  public User getAuthor() {
    return mAuthor;
  }

  public ForumPost(User author, String title, String description) {

    mTitle = title ;
    mDescription = description ;
  }

  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) {
    // TODO:  Set the private fields here
    mFirstName = firstName; 
    mLastName = lastName ;
  }

  public String getFirstName(){
    return mFirstName;
  }

  public String getLastName(){
    return mLastName;
  }

}
Forum.java
public class Forum {
  private String mTopic;

  public String getTopic() {
      return mTopic;
  }

  public Forum(String Topic){

    mTopic = Topic ;
  }

  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(args[0], args[1]);
    //author(args[0], args[1]); 
    // Add the author, title and description
     ForumPost post = new ForumPost(author, args[0],args[1]);
    //post(author, "Kantimoy","amazing");
      forum.addPost(post);
  }
}
Jordan Ernst
Jordan Ernst
5,121 Points

i am having the exact same problem let me know if you get this resolved i did this challenge 3 times and it just says oops. we encountered a problem after telling me there is a null pointer.

2 Answers

samuel zaffran
samuel zaffran
24,815 Points

Hi,

I think the problem come from here :

public ForumPost(User author, String title, String description) {

mTitle = title ;
mDescription = description ;

}

I let you think about it, you almost get it ! Something missing, you set title and description already.. Luck.

Jordan Ernst
Jordan Ernst
5,121 Points

the hint is in the instructions, they introduced a bug in your code. i realized this when reading through the lines i noticed what i had set in my ForumPost constructor was gone. you will see the error and finally be on your way the guy before me is right!