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Java Java Data Structures Exploring the Java Collection Framework Maps

Posted by Felipe Murillo
Felipe Murillo
3,605 Points

Stuck in MAP section of Java Data Structures

Not sure what other steps to take to make this work. Any hints?

Thanks!

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.*;

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(String category, Integer count){
    Map <String, Integer> categoryCount= new HashMap <String, Integer>();
   for ( BlogPost post: getPosts()){
      category= post.getCategory();
     if (post.getCategory()==null){
       count=0; 
     }
     count++;
     categoryCount.put(category, count);
   }
    System.out.println(categoryCount);
   return categoryCount;
  }
}

1 Answer

Ronald Williams
seal-mask
.a{fill-rule:evenodd;}techdegree seal-36
Ronald Williams
Java Web Development Techdegree Graduate 25,021 Points
Ronald Williams
.a{fill-rule:evenodd;}techdegree seal-36
Ronald Williams
Java Web Development Techdegree Graduate 25,021 Points 
/*
This method does not need to take in a String category and Integer Count. 
The method should take in nothing and return a map.
At the top of the class Blog.java there is a List of BlogPost called mPosts. 
We will inspect those.
*/

public Map<String, Integer> getCategoryCounts() {
    Map <String, Integer> categoryCount= new HashMap <String, Integer>();
//Inspecting the blogposts at the top of Blog.java
    for ( BlogPost post : mPosts) {
//if the post is not null AND the map we made does not already contain this category
      if (post.getCategory() != null && !categoryCount.containsKey(post.getCategory())) {
//Add the category and make the count 1
         categoryCount.put(post.getCategory(), 1);
//Else if the map we made already has this category. i.e. multiple posts with category "Java"
      } else if (categoryCount.containsKey(post.getCategory())) {
 /*
We will replace the category and change the value for count + 1
Note: there is probably an easier way to do this but this works
*/
        categoryCount.replace(post.getCategory(), categoryCount.get(post.getCategory()) + 1);
      }
    }
    return categoryCount;
  }
Felipe Murillo
Felipe Murillo
3,605 Points

Thanks!!