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Java Java Data Structures - Retired Exploring the Java Collection Framework Sets

Alex Lowe
Alex Lowe
15,147 Points
Posted by Alex Lowe
Alex Lowe
15,147 Points

Having Trouble with Challenge

If I understand this correctly, I'm supposed to loop through each BlogPost in a Blog and return a Set of all of the authors. I'm not sure either how to get the authors, or how to loop through the blog posts. Do I need to make a separate getAuthors method?

EDIT: I've updated my code. I think I'm closer, no errors this time, but it's asking if I created a public method called getAllAuthors.

com/example/BlogPost.java 
package com.example;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;


public class BlogPost implements Comparable<BlogPost>, Serializable {
  private String mAuthor;
  private String mTitle;
  private String mBody;
  private String mCategory;
  private Date mCreationDate;

  public BlogPost(String author, String title, String body, String category, Date creationDate) {
    mAuthor = author;
    mTitle = title;
    mBody = body;
    mCategory = category;
    mCreationDate = creationDate;
  }

  public int compareTo(BlogPost other) {
    if (equals(other)) {
      return 0;
    }
    return mCreationDate.compareTo(other.mCreationDate);
  }

  public String[] getWords() {
    return mBody.split("\\s+");
  }

  public List<String> getExternalLinks() {
    List<String> links = new ArrayList<String>();
    for (String word : getWords()) {
      if (word.startsWith("http")) {
        links.add(word);
      }
    }
    return links;
  }

  public String getAuthor() {
    return mAuthor;
  }

  public String getTitle() {
    return mTitle;
  }

  public String getBody() {
    return mBody;
  }

  public String getCategory() {
    return mCategory;
  }

  public Date getCreationDate() {
    return mCreationDate;
  }
}
com/example/Blog.java 
package com.example;

import java.util.List;
import java.util.Set;
import java.util.HashSet;
import java.util.TreeSet;

public class Blog {
  List<BlogPost> mPosts;

  public Blog(List<BlogPost> posts) {
    mPosts = posts;
  }

  public List<BlogPost> getPosts() {
    return mPosts;
  }

  public Set<String> getAllAuthors(List<BlogPost> posts){
    Set<String> allAuthors = new TreeSet<String>();
    for (BlogPost bp : posts){
      allAuthors.add(bp.getAuthor());
  }
    return allAuthors;
}
}

2 Answers

David Axelrod
David Axelrod
36,073 Points
David Axelrod
David Axelrod
36,073 Points

Ahhh 3 things

Dont think you need to import HashSet

Get all authors shouldnt take a parameter

in your for loop, you are pulling from posts which isnt available to the class. You have to use mPosts

hope this helps!!

public Set<String> getAllAuthors(){
    Set<String> allAuthors = new TreeSet<String>();
    for (BlogPost bp : mPosts){
      allAuthors.add(bp.getAuthor());
  }
    return allAuthors;
}
Alex Lowe
Alex Lowe
15,147 Points
Alex Lowe
Alex Lowe
15,147 Points

Thanks, that worked.