Welcome to the Treehouse Community

The Treehouse Community is a meeting place for developers, designers, and programmers of all backgrounds and skill levels to get support. Collaborate here on code errors or bugs that you need feedback on, or asking for an extra set of eyes on your latest project. Join thousands of Treehouse students and alumni in the community today. (Note: Only Treehouse students can comment or ask questions, but non-students are welcome to browse our conversations.)

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and a supportive community. Start your free trial today.

Java Java Objects Delivering the MVP Forum

Vlad Gheorghe
Vlad Gheorghe
1,987 Points

My code doesn't compile (task 4)

Oddly, the error points back to earlier code:

./Forum.java:10: error: invalid method declaration; return type required public setTopic(String topic) { ^ Note: JavaTester.java uses unchecked or unsafe operations. Note: Recompile with -Xlint:unchecked for details. 1 error

Forum.java
public class Forum {
  private String topic;

  // TODO: add a constructor that accepts a topic and sets the private field topic

  public String getTopic() {
    return topic;
  }

  public setTopic(String topic) {
    this.topic = topic;
  }


  public void addPost(ForumPost post) {
    System.out.printf("A new post in %s topic from %s %s about %s is available",
            topic,
            post.getAuthor().getFirstName(),
            post.getAuthor().getLastName(),
            post.getTitle()
    );
  }

}
User.java
public class User {
  // TODO: add private fields for firstName and lastName
  private String firstName = "";
  private String lastName = "";

  public User(String firstName, String lastName) {
    // TODO: set and add the private fields
    this.firstName = firstName; 
    this.lastName = lastName;
  }

  // TODO: add getters for firstName and lastName
  public String getFirstName() {
    return firstName;
  }

  public String getLastName() {
    return lastName;
  }

}
ForumPost.java
public class ForumPost {
  private User author;
  private String title;
  private String description;

  // TODO: add a constructor that accepts the author, title and description

  public User getAuthor() {
    return author;
  }

  public String getTitle() {
    return title;
  }

  public String getDescription() {
    return description;
  }

  public ForumPost (User author, String title, String description) {
    this.author = author;
    this.title = title; 
    this.description = description;
  }
}
Main.java
public class Main {

  public static void main(String[] args) {
    System.out.println("Beginning forum example");
    if (args.length < 2) {
      System.out.println("Usage: java Main <first name> <last name>");
      System.err.println("<first name> and <last name> are required");
      System.exit(1);
    }

    Forum forum = new Forum("Java");
    // TODO: pass in the first name and last name that are in the args parameter
    User author = new User(args[0], args[1]);
    // TODO: initialize the forum post with the user created above and a title and description of your choice
    ForumPost post = new ForumPost(author, "title", "description");
    forum.addPost(post);


  }

}

2 Answers

andren
andren
28,520 Points

It's only in the last task that the code checker actually tries to run your code for real, before then it just runs some checks where it tries to verify that your code looks correct.

The first task asks you to add a constructor to the Forum class. But you have actually added a setter method instead.

The difference between a constructor and a regular method is that a constructor's name has to match the name of the class exactly, and it does not require a return type. If you rename the method like this:

public Forum(String topic) {
    this.topic = topic;
}

Then your code will work.

Vlad Gheorghe
Vlad Gheorghe
1,987 Points

Ok so I actually had to call it public Forum. Thanks

andren
andren
28,520 Points

Ops you are right. I mixed up the name of the field variable and the class in the code example. Sorry about that. I've now edited the name to the correct one.

Vlad Gheorghe
Vlad Gheorghe
1,987 Points

Sure, I understood anyway!