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Java Java Objects Delivering the MVP Forum

Supattra Manaphongphan
Supattra Manaphongphan
935 Points
Posted by Supattra Manaphongphan
Supattra Manaphongphan
935 Points

This seems like a bug: Bummer! Make sure you uncomment the code in Main.java at Wrapping 4/4

I've been trying to get through this but I keep getting this error even though I'm sure I have uncommented everything. Anyone else experiencing this? Thank you so much

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){
  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
this.firstName = firstName;
this.lastName = lastName;
  }
public String getFirstName() {
  return firstName;
}
  public String getLastName() {
  return lastName;
}


  // TODO: add getters for firstName and 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) {
  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(author, "title", "description");
    Forum.addPost(post);

  }

}

1 Answer

Isaiah Marin
Isaiah Marin
11,971 Points
Isaiah Marin
Isaiah Marin
11,971 Points

Hey, I noticed many of your constructors are not initializing the private member correctly. For example: "topic = this.topic;" needs to be "this.topic = topic;"

I posted each code for each task that worked for me.

Task 1: The first part you want to code a constructor of the Forum class.

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

Task 2: You have some private variables and initialize them in the constructor. And then you make getter methods to return the private variables.

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 this.firstName;
  }
  public String getLastName() {
    return this.lastName;
  }
}

Task 3:

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;
  }
}

Task 4: You want to make the Forum class is un-commented and the main.

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);
  }

}
Supattra Manaphongphan
Supattra Manaphongphan
935 Points
Supattra Manaphongphan
Supattra Manaphongphan
935 Points

Hi Isaiah,

You saved me. It worked! Thank you so much :)