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Java Java Objects Delivering the MVP Forum

Leo Marco Corpuz
Leo Marco Corpuz
18,975 Points

I have no idea how to do the last part of this challenge.

I have no idea how to do this part of the challenge. I'm lost. I've tried to solve this but it doesn't make any sense.

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
private 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();
    // TODO: initialize the forum post with the user created above and a title and description of your choice
   this.lastName=lastName;

    ForumPost post = new ForumPost();
    forum.addPost(post);


  }

}

2 Answers

Daniel Turato
seal-mask
PLUS
.a{fill-rule:evenodd;}techdegree seal-36
Daniel Turato
Java Web Development Techdegree Graduate 30,124 Points

Here's what I got for Main.java, this should work:

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, "TestTitle", "TestDesc");
    forum.addPost(post);

  }

}

When passing arg's in java through the Main method, it puts it into a String array. In this case, the firstName and lastName are passed into the 1st and 2nd elements of the string array. To access them, all you have to do is go args[?] where the ? represents the specific index you want. Hope this helps

Leo Marco Corpuz
Leo Marco Corpuz
18,975 Points

Thanks!

But can you explain this line of code from the Forum class: post.getAuthor().getFirstName(), post.getAuthor().getLastName() How is the getFirstName and getLastName method being accessed without the User class and I don't understand how they're combining different methods through dot notation.

Daniel Turato
seal-mask
PLUS
.a{fill-rule:evenodd;}techdegree seal-36
Daniel Turato
Java Web Development Techdegree Graduate 30,124 Points

Well the first thing they did was this:

post.getAuthor();

What this does is access the Forum Post object and then calls the getAuthor() method. This method then returns a User object which is the user who created the post. From there you can do this:

getFirstName();

This will then return the first name of the User using the getFirstName() method.