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

Timothy Williams
Timothy Williams
1,536 Points
Posted by Timothy Williams
Timothy Williams
1,536 Points

my getAllAuthors is failing to compile

I'm not fully grasping Sets, Lists, etc pffft! Help

package com.example;

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

public class Blog {
  List<BlogPost> mPosts;

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

  public List<BlogPost> getAllAuthors() {
    Set<String> allAuthors = new TreeSet<String>();
    for (BlogPost blogpost:mPosts){
    allAuthors.addAll(blogpost.getAuthor());
    }
    return allAuthors;
  }

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

1 Answer

Dan Johnson
Dan Johnson
40,533 Points
Dan Johnson
Dan Johnson
40,533 Points

The addAll method is for adding an entire collection (anything implementing this interface) to the Set. You can use add for single items.

Other than that you just need to change your return value to the appropriate type.

Rulon Taylor
Rulon Taylor
2,762 Points

Thanks for this response. It was what I needed to get going!