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

Olha Markova
Olha Markova
2,050 Points

I am stuck with this chellange

I get an error "Can not find symbol" in the line for (String category : post.getCategoryCounts()){ I have no idea what is wrong

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 category : post.getCategoryCounts()){
  Integer count = categoryCounts.get(category);
    if (count == null){
    count = 0;
    }
    count ++;
    categoryCounts.put(category, count);
  }
    return categoryCounts;
    }
  }
}

1 Answer

Brendan Whiting
seal-mask
.a{fill-rule:evenodd;}techdegree seal-36
Brendan Whiting
Front End Web Development Techdegree Graduate 84,738 Points

On line 31 you’re trying to call a getCategoryCounts() method on the blog post, but blogposts don’t have that method. (This is the name of the method we’re trying to make on the Blog not the BlogPost). I don’t think you need the 2nd for loop here. You just want to grab the blog post’s category with its getCategory method and put it in a variable, and then the rest of your code is good.

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;
  }