what am i doing wrong in main.java?

Question

./Main.java:13: error: cannot find symbol User author = new User(firstName, lastName); ^ symbol: variable firstName location: class Main ./Main.java:13: error: cannot find symbol User author = new User(firstName, lastName); ^ symbol: variable lastName location: class Main ./ForumPost.java:6: error: cannot find symbol mAuthor = author; ^ symbol: variable mAuthor location: class ForumPost ./ForumPost.java:7: error: cannot find symbol mTitle = title; ^ symbol: variable mTitle location: class ForumPost ./ForumPost.java:8: error: cannot find symbol mDescription = description; ^ symbol: variable mDescription location: class ForumPost Note: JavaTester.java uses unchecked or unsafe operations. Note: Recompile with -Xlint:unchecked for details. 5 errors

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 Forum(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;    
  }
 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;
public ForumPost(User author, String title, String description) {
    mAuthor = author;
    mTitle = title;
    mDescription = 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;
  }
}

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");
    // Take the first two elements passed args
    User author = new User(firstName, lastName);
    // Add the author, title and description
    ForumPost post = new ForumPost(author, "This is your forum post Title", 
                                           "This is your forum post Description");
    forum.addPost(post);

// */
  }

}

Answer 1 · 2018-01-06T02:38:08Z

January 6, 2018 2:38am

Hi Abdurahman,

You're very close.

The first issue I found was in your ForumPost.java. You are setting properties in your ForumPost method that aren't associated with anything.

Yours

public ForumPost(User author, String title, String description) {
    mAuthor = author;
    mTitle = title;
    mDescription = description;
}

Should Be

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

As for your Main.java, this is very close. The issue lies here:

// Take the first two elements passed args
    User author = new User(firstName, lastName);

Take special note of the comment. It says "Takes the first two elements passed args". Mine said "// TODO: pass in the first name and last name that are in the args parameter" but that's similar enough. What it means is that you should be taking the first two elements from the args array. So args[0] and args[1].

Your code will look like this:

// TODO: pass in the first name and last name that are in the args parameter
    User author = new User(args[0], args[1]);

Hope this helps!

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Abdurahman Osman

Abdurahman Osman

what am i doing wrong in main.java?

1 Answer

David Evans

David Evans