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Start your free trialMatt Adams
4,856 PointsKeep getting incorrect category counts
I continue to get incorrect category counts. Here is my code:
package com.example;
import java.util.HashSet; import java.util.HashMap; import java.util.List; import java.util.Map; import java.util.Set; import java.util.TreeSet;
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>(); Set<String> categories = new TreeSet<>(); for (BlogPost post : mPosts) { categories.add(post.getCategory()); for (String category : categories) { Integer count = categoryCounts.get(category); if (count == null) { count = 0; } count++; categoryCounts.put(category, count); } } return categoryCounts; } }
I've tried a few different variations here, including un-nesting the second 'for' loop in the getCategoryCounts, and using a HashSet instead of a TreeSet for the 'categories' variable. Any advice?
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;
}
}
package com.example;
import java.util.List;
import java.util.Set;
import java.util.TreeSet;
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;
}
}
1 Answer
Grigorij Schleifer
10,365 PointsHi Matt,
here is a commented code suggestion:
public Map<String, Integer> getCategoryCounts() {
Map<String, Integer> categoryCount = new HashMap<String, Integer>();
// create a Map that accepts a String as key and an Integer as value
// so the key is the category (as String)
// and value is the count how many categories are in the post (as Integer)
// no need to create an extra Set for categories
for(BlogPost post: mPosts) {
// loop over every post in mPosts (you got it right)
// you can examen every post later
// no need for a second for loop
String category = post.getCategory();
// "extract" the category name and (store it into a String) from the post
Integer count = categoryCount.get(category);
// create new count Integer to store the number of categories
// proof whether a category is avalable in your post using getCategory() method
// getCategory returns a null if no category avalable in the map
if(count == null) {
// so if count is null, there is no category in the Map yet
count = 0;
// set count to 0
}
count++;
// increment if getCategory returns not null (there is a category in the map)
categoryCount.put(category, count);
// put category as key and count as value in Map
}
return categoryCount;
}
I hope I could help a little bit.
Grigorij
Matt Adams
4,856 PointsMatt Adams
4,856 PointsThis is fantastic, thanks for your help Grigorij!
Grigorij Schleifer
10,365 PointsGrigorij Schleifer
10,365 PointsHey Matt,
I am glad I could help:)