Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

Java Java Data Structures Exploring the Java Collection Framework Sets

Posted by Jakub Szczepanik
Jakub Szczepanik
10,194 Points

Hey this code doesn't run for me. All the time it's showing that I haven't done all the imports I should.

What should I add here? It's still showing me problems with imports.

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.TreeSet;

import com.example.BlogPost;

public class Blog {
  List<BlogPost> mPosts;

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

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

  public List<BlogPosts> getAllAuthors() {
    Set<String> allPosts = new TreeSet<String>();
     for(String word: getPosts()) {
      if(word.equals(mAuthor)) { 
        allPosts.getAuthor(word);
      }
    }
    return allPosts;
  }

}

1 Answer

Thomas Nilsen
Thomas Nilsen
14,957 Points
Thomas Nilsen
Thomas Nilsen
14,957 Points

Your version:

public List<BlogPosts> getAllAuthors() {
    Set<String> allPosts = new TreeSet<String>();
     for(String word: getPosts()) {
      if(word.equals(mAuthor)) { 
        allPosts.getAuthor(word);
      }
    }
    return allPosts;
  }

The following things needs changing:

  • The method should return a Set, not a List
  • In you for loop, you're looping over BlogPosts objects, but you write String
  • No need for a if-check, you're just supposed to loop over everything and add it to the Set

Here is the correct version

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