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 - Retired Exploring the Java Collection Framework Sets

heres how far i got

still not knowing what to do

2 Answers

package com.example;

import java.util.List;
import java.util.Set;
import java.util.SortedSet;
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() {
    SortedSet<String> authors = new TreeSet<>();
    for (BlogPost post : mPosts) {
      authors.add(post.getAuthor());
    }
    return authors;
  }
}

A Set is a unique collection of Objects. A TreeSet is an ordered collection (it implements the Set interface). So just adding Strings to a TreeSet will order them alphabetically.