Need some help

Question

how to make correlation between count and category

public Map<String,Integer> getCategoryCounts() { Map<String, Integer> categories = new HashMap<String, Integer>(); for (BlogPost post: mPosts) { Integer count; if (count == null) { count = 0; } count++; categories.put(post.getCategory(), count); } }

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

}

Answer 1 · 2018-03-12T13:04:10Z

March 12, 2018 1:04pm

Hi Zuzanna...

You almost done it. You just need a little revision in your code. As you said yourself you need to connect the count to the category. But in this case it will be appropriate to say how to get the initial count to be processed. This is where you need a Map method called get please spare some times to review it in java doc here. This method will return the value of count if it is already exist and null of it has not being instantiated (or being made before). This is the only revisione you need to make in your code oh that and also you need to return the Map:

public Map<String,Integer> getCategoryCounts() {
    Map<String, Integer> categories = new HashMap<String, Integer>();
    for (BlogPost post: mPosts) {
      Integer count = categories.get(post.getCategory());//<- this is the only revision you need to make
      if (count == null) {
        count = 0;
      }
      count++;
      categories.put(post.getCategory(), count);
    }
     return categories;//<- do not forget to return the Map you made.
  }

Basically if the Integer count = categories.get(post.getCategory()) is null then it means you have not count this particular category, meaning you need to count from zero right? That is what the IF statement is there for. Then for the others since it is already mapped you just need to call Integer count = categories.get(post.getCategory()); from the map. Then increment the count by count++ and put it back into the map using : categories.put(post.getCategory(), count);

After you done looping all BlogPost posts then you need to return the Map you just made

I hope this can help a little

Welcome to the Treehouse Community

Looking to learn something new?

Zuzanna Kulej

Zuzanna Kulej

Need some help

1 Answer

Yanuar Prakoso

Yanuar Prakoso