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Java Java Objects (Retired) Delivering the MVP Wrapping up

MSG: Did you not uncomment the Forum.addPost method? It appears to not being called properly in Forum.java.

Iยดm getting this message but this method is uncommented, as you can see in the code

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

  public User getAuthor() {
    return mAuthor;
  }

  public String getTitle() {
    return mTitle;
  }
public String getDescription() {
  return mDescription;
}
  public ForumPost(User author, String title, String description){
    }
}
User.java
public class User {
  private String mFirstName;
  private String mLastName;

  public User(String firstName, String lastName) {
      mFirstName = firstName;
      mLastName = lastName;
  }

  public void setFirstName(String firstName) {
       mFirstName = firstName;
  }

  public void setLastName(String lastName) {
       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 void addPost(ForumPost post) {
      /* When all is ready uncomment this...
      System.out.printf("New post from %s %s about %s.\n",
                         post.getAuthor().getFirstName(),
                         post.getAuthor().getLastName(),
                         post.getTitle());
      */
  }
  public Forum(String topic){
    mTopic = topic;

  }
}
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]);
    // Add the author, title and description
     ForumPost post = new ForumPost(author, "Rafael", "Awesome" );
     forum.addPost(post);
  }
}

4 Answers

anil rahman
anil rahman
7,786 Points

Try uncommenting that code within the method.

anil rahman
anil rahman
7,786 Points
  public void addPost(ForumPost post) {
      /* When all is ready uncomment this...
      System.out.printf("New post from %s %s about %s.\n",
                         post.getAuthor().getFirstName(),
                         post.getAuthor().getLastName(),
                         post.getTitle());
      */
  }

Give this error: Starting forum example... java.lang.NullPointerException at Forum.addPost(Forum.java:12) at Example.main(Example.java:13) at JavaTester.run(JavaTester.java:183) at JavaTester.main(JavaTester.java:43)

I have tried to reset the code, paste the correct answer that someone posted before... no one works

When I uncomment this part, give this error:

Starting forum example... java.lang.NullPointerException at Forum.addPost(Forum.java:12) at Example.main(Example.java:13) at JavaTester.run(JavaTester.java:183) at JavaTester.main(JavaTester.java:43)

anil rahman
anil rahman
7,786 Points

Try this:

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

//add these in the constructor to actually make sure your variables are being stored
   author  = mAuthor;
   title = mTitle;
   description = mDescription;
}

Still getting the same error: NullPointerException

Solved with : public ForumPost(User author, String title, String description){ mAuthor = author; mTitle = title; mDescription = description;