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 Maps

jinhwa yoo
jinhwa yoo
10,042 Points
Posted by jinhwa yoo
jinhwa yoo
10,042 Points

I got stuck

what 's wrong ??

Jason Anello
Jason Anello
Courses Plus Student 94,610 Points

Hi jinhwa,

What code are you trying?

2 Answers

Jason Anello
Jason Anello
Courses Plus Student 94,610 Points

Your method looks good but you forgot to import Map and HashMap

import java.util.Map;
import java.util.HashMap;
jinhwa yoo
jinhwa yoo
10,042 Points
jinhwa yoo
jinhwa yoo
10,042 Points

In Blog.java add a new method called getCategoryCounts. It should return a Map of category to count calculated by looping over all the posts.

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> getPosts() {
    return mPosts;
  }

  public Set<String> getAllAuthors() {
    Set<String> authors = new TreeSet<>();
    for (BlogPost post: mPosts) {
      authors.add(post.getAuthor());
    }
    return authors;
  }
    public Map<String, Integer> getCategoryCounts() {
    Map<String, Integer> categoryCounts = new HashMap<String, Integer>();
    for (BlogPost post : mPosts) {
        String category = post.getCategory();
        Integer count = categoryCounts.get(category);
        if (count == null) {
          count = 0;
        }
        count++;
        categoryCounts.put(category, count);
    }
    return categoryCounts;
  }
}