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

pratham daswani
pratham daswani
979 Points

maps

now i did this ,what's the bug in this now?, some code would be very helpful.

com/example/BlogPost.java
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;
  }
}
com/example/Blog.java
package com.example;

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

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> catCount = new HashMap<String,Integer>();
    for (BlogPost post: mPosts) {
      for(String category : post.getCategory())
      {
        Integer count = catCount.get(category);
        if(count == null)
        {
          count = 0;

        }
        count++;
        catCount.put(category,count);
      }
    }

  }
}
pratham daswani
pratham daswani
979 Points

It shows an error that getCategory() method cannot be used.

1 Answer

Kourosh Raeen
Kourosh Raeen
23,733 Points

In the inner for loop, you are looping over post.getCategory() but post.getCategory() returns a single String. Each post has a single category so you don't need the inner loop. Also, when you're done with the loop you need to return catCount.

pratham daswani
pratham daswani
979 Points

In the inner for loop, I am looping over post.getCategory() but post.getCategory() returns a single String, but sir isn't that what I am supposed to do? The Question says "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." So don't I need to find the count for each single category? Is there any other way to do this? Yes I need to return catCount.

Can you explain with some code?

Kourosh Raeen
Kourosh Raeen
23,733 Points

You cannot loop over a single item. Yes, you need to find the category count for each single category, but you do that by looping over the posts. You can reuse a lot of the code you already have, like the outer loop and the if statement and the code following the id statement. What you need to change is the variable category, since after deleting the inner loop it would exist anymore. You can simply replace the variable category with post.getCategory(). Make these changes and if it doesn't pass post your code here.

pratham daswani
pratham daswani
979 Points

I get Your point , but then in the put statement " catCount.put(category,count); " what do I put category as?

Kourosh Raeen
Kourosh Raeen
23,733 Points

Use post.getCategory() instead of category.