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Java Java Data Structures - Retired Exploring the Java Collection Framework Sets

Aaron Coursolle
Aaron Coursolle
18,014 Points

Was not sure what to loop through in the "for" line of code

Code attached:

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;

public class Blog {
  List<BlogPost> mPosts;

  public Blog(List<BlogPost> posts) {
    mPosts = posts;
  }

  public List<BlogPost> getPosts() {
    return mPosts;
  }
  Set<String> getAllAuthors = new TreeSet<String> ();
  for (Post post : posts) {
   getAllAuthors.addAll(post.getAllAuthors());
  }
  System.out.println("Authors: %s %n", getAllAuthors);
}

1 Answer

Kourosh Raeen
Kourosh Raeen
23,733 Points

Hi Aaron - You need to define the function first:

public Set<String> getAllAuthors() {

}

Then inside the function you can define your TreeSet and write the loop. A few more points:

  1. The posts are in mPosts not posts.

  2. The loop variable post should be of type BlogPost, not Post since we don't have a class called Post.

  3. The BlogPost class does not have a method called getAllAuthors(). However, there is the method getAuthor() that you can call on post and then add the returned author to your TreeSet using the add() method.