See below thread

First I realized that the "Blog" class constructor wants a list, but you are giving it several other parameters instead :)

After that, I checked the actual code challenge description. Basically, you should create a "getAllAuthors" method in the "Blog" class, which handles "BlogPost" objects. But you, instead, tried to do this the other way around. You tried to put it into the "BlogPost" class, and tried to handle "Blog" objects.

I hope this helps. If you still struggle, feel free to ask further questions. If I might not notice, contact me here: http://facebook.com/puklibalazs

Yeah. Must have been sleepy. Got something backwards.

Why is this answer wrong? public Set getAllAuthors() { Set<String> authors = new TreeSet<String>(); for(BlogPost post : mPosts ) { authors.add(post.getAuthor()); } return authors; }

Error says: " Bummer! You should be using a Generic type, specifically Set<String>. You returned a java.util.Set"

Instruction says.. returns a java.util.Set

You can not return a "Set", you have to return a "Set of something" only :D the method declaration will start like this:

public Set<String> getAllAuthors() {......etc

Gotcha