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Java Java Objects Delivering the MVP Forum

Rebecca Fuller
Rebecca Fuller
7,990 Points

Java Objects: Forum: Task 4 of 4 - Error Message

I'm not understanding why I keep getting this error message, I haven't even changed this line of code...

Forum.java
public class Forum {
  private String topic;

  // TODO: add a constructor that accepts a topic and sets the private field topic
  public void getTopic (String topic) {
    topic = this.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
    firstName = this.firstName;
    lastName = this.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 void getInfo(User author, String title, String description) {
    author = this.author;
    title = this.title;
    description = this.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();
    forum.addPost(post);

  }

}
Rebecca Fuller
Rebecca Fuller
7,990 Points

Sorry forgot to include the error message:

./Main.java:10: error: constructor Forum in class Forum cannot be applied to given types; Forum forum = new Forum("Java"); ^ required: no arguments found: String reason: actual and formal argument lists differ in length Note: JavaTester.java uses unchecked or unsafe operations. Note: Recompile with -Xlint:unchecked for details. 1 error

1 Answer

ofir moalmi
ofir moalmi
2,161 Points

I'm new to java as well so Im not too sure but I did notice that you dont have a constructor, add constructors where needed, for the Forum class its public Forum(String topic){ topic = this.topic;

}

and same goes for your ForumPost class.

edit: I just tried out the challnge aswell and got stuck, and apparently what caused the errors is using variable = this.variable; instead of this.variable = variable; im still having confusion about what this. actually refers to.

and you also don't have an parameters in your ForumPost post object.