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Java Java Data Structures Exploring the Java Collection Framework Maps

Dozie Anazia
Dozie Anazia
1,227 Points
Posted by Dozie Anazia
Dozie Anazia
1,227 Points

getCategoryCounts Everything is correct except for the return statement.

I've done everything I could, but I'm not sure where I went wrong. Apparently I'm missing the return statement according to the compiler error, but I'm not sure where to put it.

Please help

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 post: mPosts) {
    for(String type: post.getWords()) {
      Integer count = categoryCounts.get(type);
      if (count == null) {
        count = 0;
      }
      count++;
      categoryCounts.put(type, count);
    }
   }
  }

}
Dozie Anazia
Dozie Anazia
1,227 Points
Dozie Anazia
Dozie Anazia
1,227 Points

So I added the return statement which was in the middle of the last 4 brackets. My return statement was // return categoryCounts; // Apparently this still isn't correct. My error reads: "Bummer: For category Entertainment, expected 1 but received null."

I'm even more confused now. this is the only error I have.

1 Answer

Linda de Haan
Linda de Haan
12,413 Points
Linda de Haan
Linda de Haan
12,413 Points

This code worked for me:

  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;
  }

Get rid of the inner for loop. The return statement usually goes at the end of the method, but not always. If a method returns a Map, the method body has to return that somewhere in its code. If you're not sure where to put a return statement, go through the method a few times using different scenario's.