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

Abhishek Gangadhar
Abhishek Gangadhar
9,467 Points
Posted by Abhishek Gangadhar
Abhishek Gangadhar
9,467 Points

Not getting the proper count!!

I am getting an error that the count of the entertainment category is 2 instead of 1. Can someone plz tell me whats the error in my code.

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> results = new HashMap<String,Integer>();
    for(BlogPost post: mPosts){
      String category = post.getCategory();
      if(results.get(category)==null){
        results.put(category,1);
      }
      int val = results.get(category);
      results.put(category,val+1);
    }
    return results;
  }
}

2 Answers

Jeremy Hill
Jeremy Hill
29,567 Points

Here is what I did to pass:

package com.example;

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

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;
  }

  // the method that I created below

  public Map<String, Integer> getCategoryCounts(){
    Integer count = 0;

    Map<String, Integer> categories = new HashMap<>();
       for(BlogPost post: mPosts){
          count = 0;
          for(BlogPost posts: mPosts){
             if(posts.getCategory().equals(post.getCategory())) {
                ++count;
             }
          }
          categories.put(post.getCategory(), count);
       }
    return categories;
  }
}
Abhishek Gangadhar
Abhishek Gangadhar
9,467 Points
Abhishek Gangadhar
Abhishek Gangadhar
9,467 Points

Thanks Jeremy, but wouldnt this be ineffiecent, you would have to loop through multiple times if there are categories repeated more times.

Abhishek Gangadhar
Abhishek Gangadhar
9,467 Points
Abhishek Gangadhar
Abhishek Gangadhar
9,467 Points

And can you plz tell me what the mistake in my code is ??/

Jeremy Hill
Jeremy Hill
29,567 Points
Jeremy Hill
Jeremy Hill
29,567 Points

Yes there are more efficient ways of doing this- I probably should have spent a little more time on this challenge to give you more efficient code.

I am reposting your code, look for my comment and make the change that I point to if you want your code to pass:

public Map<String,Integer> getCategoryCounts(){
    Map<String,Integer> results = new HashMap<String,Integer>();
    for(BlogPost post: mPosts){
      String category = post.getCategory();
      if(results.get(category)==null){
        results.put(category,1);          // change this integer to 0:  results.put(category, 0);
      }
      int val = results.get(category);
      results.put(category,val+1);
    }
    return results;
  }