Welcome to the Treehouse Community
Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.
Looking to learn something new?
Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.
Start your free trialRik-Jan van Bree
1,084 PointsHi, in task 4 of 4, I get a java.lang.NullPointerException at line 15 in class Forum.Java. Can you help me? Thx.
Hi, in challenge 4, I get a null-point exception at line 14 in class Java. Can you help me? Thx.
Here is the code:
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 author1 = new User("Rik-Jan","vanBree"); // Add the author, title and description ForumPost post = new ForumPost(author1 ,"Lean","mgmtsubject"); forum.addPost(post); } }
Forum.Java: public class Forum { private String mTopic;
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());
} }
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; } }
Forumpost.java public class ForumPost { private User mAuthor; private String mTitle; private String mDescription;
public User getAuthor() { return mAuthor; }
ForumPost (User author, String title, String description){ User mAuthor=author; mTitle = title; mDescription = description; }
public String getDescription(){ return mDescription; }
public String getTitle() { return mTitle; } }
public class ForumPost {
private User mAuthor;
private String mTitle;
private String mDescription;
public User getAuthor() {
return mAuthor;
}
ForumPost (User author, String title, String description){
User mAuthor=author;
mTitle = title;
mDescription = description;
}
public String getDescription(){
return mDescription;
}
public String getTitle() {
return mTitle;
}
}
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;
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 < 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 author1 = new User("Rik-Jan","vanBree");
// Add the author, title and description
ForumPost post = new ForumPost(author1 ,"Lean","mgmtsubject");
forum.addPost(post);
}
}
2 Answers
Jeremy Hill
29,567 PointsI was going to try to pick through your code but because there was so much I figured I would show you mine: It was relatively easy as far as following the instructions. There was just one step that tripped me up- trying to figure out who the authors were supposed to be. I just added the built in args[] to add the users. That actually lets the user type in those parts when they run the program. Anyway just take a look:
// ForumPost***********************************************
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
}
// end ForumPost****************************************************
// class User*******************************************************
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;
}
}
// end class User*****************************************************
// class Forum********************************************************
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());
}
}
// end class Forum********************************************************
// class Example**********************************************************
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, "Hey what's up?", "This course rocks!");
forum.addPost(post);
}
}
// end class Example**************************************************************
Rik-Jan van Bree
1,084 PointsThx a lot. It works!!
Jeremy Hill
29,567 PointsNo problem, I'm glad you got it :)