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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.

I´m 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;