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Java Java Objects Delivering the MVP Forum

Posted by Eugene Paitoo
Eugene Paitoo
3,922 Points

Main.java

Hello, Please i need a little bit of explanation with this challenge (Main.java). It will be very helpful to me.

Thanks!
Forum.java 
public class Forum {
  private String topic;


  // TODO: add a constructor that accepts a topic and sets the private field topic
  public forum(String topic) {
    this.topic = topic;
  }

  public String getTopic() {
    return 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 ForumPost(User author, String title, String description) {
    this.author = author;
    this.title = title;
    this.description = description;
  }

  public User getAuthor() {
    return author;
  }

  public String getTitle() {
    return title;
  }

  public String getDescription() {
    return 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, "Sample title", "Sample description");

    forum.addPost(post);

  }

}
Eugene Paitoo
Eugene Paitoo
3,922 Points

This is the error message I get:

/Forum.java:6: error: invalid method declaration; return type required public forum(String topic) { ^ Note: JavaTester.java uses unchecked or unsafe operations. Note: Recompile with -Xlint:unchecked for details. 1 error

1 Answer

andren
andren
28,558 Points
andren
andren
28,558 Points

There are two issues with your code and both of them are in the Forum.java file.

Constructors needs to be named exactly the same as the class they belong to, and their name is case-sensitive. Since the class is named Forum the constructor has to be named that as well. You have named the constructor forum.

When the constructor's name does not match the class it will be treated like a normal method, and normal methods requires return types, which is why you are receiving an error about a missing return type.

Also you have not removed the */ symbol used to close a multi-line comment that is found below the addPost method. Leaving that in the code will cause an error.

If you fix both of those issues like this:

public class Forum {
  private String topic;


  // TODO: add a constructor that accepts a topic and sets the private field topic
  public Forum(String topic) { // forum changed to Forum
    this.topic = topic;
  }

  public String getTopic() {
    return 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()
    );
  }
  // Trailing end multi-line comment symbol removed

}

Then your code will pass.