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

Posted by Timothy Hilley
Timothy Hilley
2,292 Points

the question itself doesnt make sense.

in this code there is only one catergory per blog post. So what am i counting? how many blog posts there are? but again that doesnt make sense because it didnt ask me to do that, it asked me to return "Category to count"... what.

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> categoryCounts = new HashMap<String, Integer>();
    for (BlogPost blogPost : mPosts) {
          String categoryName = blogPost.getCategory();
           Integer count = categoryCounts.get(categoryName);
           if(count == null) {
                 count = 0;
               }
           count++;
           categoryCounts.put(categoryName, count);
    }
  }
  }
}

2 Answers

andren
andren
28,558 Points
andren
andren
28,558 Points

You are counting the number of times a category has been used for a post. If there are five blog posts and three of them are categorized as "Java" and two as "C#" then you should return a map that looks like this:

Java: 3
C#: 2

And your code is actually doing pretty much exactly what the question is asking for. You just have two small code issues:

  1. You have somehow ended up with an extra ending } brace that does not belong in your code.

  2. You have forgotten to return the map.

If you remove one of your ending braces and add a return statement like this:

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> categoryCounts = new HashMap<String, Integer>();
    for (BlogPost blogPost : mPosts) {
          String categoryName = blogPost.getCategory();
           Integer count = categoryCounts.get(categoryName);
           if(count == null) {
                 count = 0;
               }
           count++;
           categoryCounts.put(categoryName, count);
    }
    return categoryCounts;
  }
}

Then your code will pass as you already have the correct logic in place.

Timothy Hilley
Timothy Hilley
2,292 Points
Timothy Hilley
Timothy Hilley
2,292 Points

honestly, i figured it out right after i posted the question. same result as yours though. thanks anyways :D