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Start your free trialChris Gauthier
Courses Plus Student 6,434 PointsSorting a set with TreeSet Datastructures
Im not sure why this challenge is not passing.
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<String>();
for ( List<BlogPost> post : getPosts() ) {
String newPost = (String) post;
authors.add(newPost);
}
return authors;
}
}
3 Answers
Chris Gauthier
Courses Plus Student 6,434 PointsGreat, that worked, thanks a lot!
Yanuar Prakoso
15,196 PointsHi There
You are making a mistake in your for loop and your way to add the author name to the Set needs some improvement.
Set<String> authors = new TreeSet<String>();
for ( List<BlogPost> post : getPosts() ) { //<-- You need to get each BlogPost (let's name it post) from List mPosts
String newPost = (String) post; //<-- this is wrong
authors.add(newPost);
}
return authors;
Here is how I propose the solution to finish the challenge:
Set<String> allAuthors = new TreeSet<> ();
for(BlogPost post : mPosts){
allAuthors.add(post.getAuthor());
}
return allAuthors;
I hope this can help a little
Chris Gauthier
Courses Plus Student 6,434 PointsHm..that code didn't pass the compiler.
I suspect its because the mPosts variable is out of scope, but I still don't see the solution.
Here's the error set:
./com/example/Blog.java:19: error: illegal start of type
for(BlogPost post : mPosts){
^
./com/example/Blog.java:19: error: ')' expected
for(BlogPost post : mPosts){
^
./com/example/Blog.java:19: error: expected
for(BlogPost post : mPosts){
^
./com/example/Blog.java:22: error: illegal start of type
return allAuthors;
^
./com/example/Blog.java:22: error: ';' expected
return allAuthors;
^
./com/example/Blog.java:19: error: cannot find symbol
for(BlogPost post : mPosts){
^
symbol: class mPosts
location: class Blog
./com/example/Blog.java:20: error: cannot find symbol
allAuthors.add(post.getAuthor());
^
symbol: variable post
location: class Blog
Note: JavaTester.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.
7 errors
Yanuar Prakoso
15,196 PointsHmmm... do your final answer looks like this?
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> allAuthors = new TreeSet<> ();
for(BlogPost post : mPosts){
allAuthors.add(post.getAuthor());
}
return allAuthors;
}
}
Your error usually because you miss one ')' or '}'