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Start your free trialAlex Kasper
1,896 PointsJava Sets - how do you get the for loop to go through all blogposts?
I'm not entirely sure how to get the for loop to go through all the blog posts. I would imagine that the getPosts method would be doing that but not sure how to get that to work to my advantage.
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> allAuthors = new TreeSet<String>();
for (getPosts) {
allAuthors.add(BlogPost.authors);
}
return allAuthors;
}
}
3 Answers
Jeremy Hill
29,567 PointsI believe your for loop needs to look like this:
for(BlogPost blogPost : mPosts)
Then just reference the variable "blogPost" or whatever you name it.
Florian Tönjes
Full Stack JavaScript Techdegree Graduate 50,856 PointsThe compiler cannot find the 'author' variable because it does not exist. The BlogPost object does have an 'mAuthor' variable, but this variable is private and can only be accessed from outside using the 'getAuthor' getter method.
public Set<String> getAllAuthors() {
Set<String> allAuthors = new TreeSet<>();
for (BlogPost blogPost : mPosts) {
allAuthors.add(blogPost.getAuthor()); // Now using the getAuthor() getter.
}
return allAuthors;
}
This code
for (BlogPost blogPost : mPosts) {
// Compound statement
}
means:
Execute the compound statement for each element of the 'mPosts' list. Assign one of the elements to the variable named 'blogPost', which is of type BlogPost, on each loop pass.
Regards, Florian
Alex Kasper
1,896 PointsThanks for the breakdown Florian! That really helped clear up a bunch, a new deeper understanding of the private variable. Now I really get what the getters are for.
Jeremy Hill
29,567 PointsHere try 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> authors = new TreeSet<String>();
for(BlogPost post : mPosts){
authors.add(post.getAuthor());
}
return authors;
}
}
Alex Kasper
1,896 PointsAlex Kasper
1,896 PointsThanks for the help. I'm still not able to pass the challenge.
The compiler is saying that it can't find the author variable. Is there a reason behind this?
Also I don't fully comprehend what this code dose
for (BlogPost blogPost : mPosts)
the for is enabling the for loop. The BlogPost blogPost is creating a object of BlogPost called blogPost. What is the is : mPosts doing?