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Start your free trialDinu Comendant
6,049 PointsMaps Code Challenge: for-each not applicable to expression type
it tells me "for-each not applicable to expression type" and it points at "for(String category : post.getCategory())" I have no clue how to solve it
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;
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<BlogPost, Integer> getCategoryCounts () {
Map<String, Integer> categoriesCount = new HashMap<String, Integer>();
for (BlogPost post : mPosts) {
for(String category : post.getCategory()) {
Integer count = categoriesCount.get(category);
if (count == null) {
count = 0;
}
count ++;
categoriesCount.put(category, count);
}
}
return categoriesCount;
}
}
3 Answers
Emmanuel C
10,636 PointsHey Dinu,
getCategory returns a String, and youre not allowed to iterate through a string, unless you call toCharArray() on it, which would allow you to iterate through each character in the string. However i dont believe thats what youre trying to accomplish.
If a BlogPost is supposed to have multiple categories, then I would suggest having a list of category in the class, and use that to iterate through them. Also List have a method called size() to get the number of items in the list.
I hope that helps, if not feel free to post some comments. Good Luck.
Steven Parker
231,108 PointsYou're pretty close here, I see only two issues:
The "getCategory" method returns the category as a string, just assign it to "category" directly (no loop needed).
And the method itself is defined as returning a "Map<BlogPost, Integer>", but the type of the object being returned is actually "Map<String, Integer>" — these need to match.
Fix those and you should pass the challenge!
Dinu Comendant
6,049 PointsThanks a lot Steven and Emmanuel! I really appreciate your swift answers! I went through! I don't feel that I grasped the whole problem with the getCategory though. I'm wondering why is it in the video the method works, and in the challenge it doesn't?
Map<String, Integer> hashTagCounts = new HashMap<String, Integer>();
for (Treet treet : treets) {
for (String hashTag : treet.getHashTags()) {
Integer count = hashTagCounts.get(hashTag);
if (count == null) {
count = 0;
}
count++;
hashTagCounts.put(hashTag, count);
}
Steven Parker
231,108 PointsThese examples are working with different structures. The "getHashTags" method returns an iterable collection (suitable for a loop), but "getCategory" returns a String.