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 trialChris Gauthier
Courses Plus Student 6,434 PointsHash Map tutorials, revision 2
Hello, there! I tried this myself again and thought this might be a little closer to the proper solution.
Can somebody help point me in the right direction?
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;
}
}
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 HashMap<String,Integer> getCategoryCounts() {
Map<String,Integer> authorMap = new HashMap<String,Integer>();
Integer count = 0;
String author;
for (BlogPost post: mPosts) {
author = post.getAuthor();
count++;
}
authorMap = put(author,count);
}
}
4 Answers
Craig Dennis
Treehouse TeacherHi Chris Gauthier !
Does this video here at this point help:
https://teamtreehouse.com/library/maps-2?t=510
There isn't a nested loop but the surrounding logic is similar.
Let me know if that helps to get you unstuck.
Chris Gauthier
Courses Plus Student 6,434 PointsThat didn't quite do it for me, do you have something else?
Craig Dennis
Treehouse TeacherThis line in particular:
authorMap .(author,count);
Is missing a method.
Also remember you need to pull the count out of the Map as well. If it is null, set it to 0.
That help?
Chris Gauthier
Courses Plus Student 6,434 PointsOne question, tho :
How do i get the count out of the map without actually filling in the map first?
ie) this code loops through the list posts and gets the author of each post:
public HashMap<String,Integer> getCategoryCounts() {
Map<String><Integer> hashCounts = new HashMap<String><Integer>();
for (BlogPost post : mPosts) {
String author = post.getAuthor();
}
However, I don't have the map yet, so i can't start looping over the map and incrementing the count of how many instances exist.
That might get me unstuck.
Thanks Chris
Craig Dennis
Treehouse TeacherSmall typo, but this code creates a new hash map.
Map<String, Integer> hashCounts = new HashMap<>();
If the key doesn't exist it will return a null
when you hashCounts.get(author)
. In the beginning nothing will exist. You are looping through the BlogPosts, and populating the map.
That make sense?
Chris Gauthier
Courses Plus Student 6,434 PointsChris Gauthier
Courses Plus Student 6,434 PointsOh, sorry, i saw that as an easy mistake. Lets try this again:
This:
Doesn't work.
Can you explain why?
Chris