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Java Java Data Structures Exploring the Java Collection Framework Sets

Shane May
Shane May
5,114 Points
Posted by Shane May
Shane May
5,114 Points

TreeSet getAllAuthors. What do I run through to get all the others? Where did I go wrong?

I believe I understand what the challenge is asking me. What I don't know is what I am suppose to loop through? And where did I go wrong in general? Any help is greatly appreciated.

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.*;

public class Blog {
  List<BlogPost> mPosts;

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

  public List<BlogPost> getPosts() {
    return mPosts;
  }

  public List<String> getAllAuthors(){
    Set<String> results = new TreeSet<String>();
    for(Blog post : mPosts){
      results.addAll(post.getAuthor());
    }
    return results;
  }

}

1 Answer

Kourosh Raeen
Kourosh Raeen
23,733 Points
Kourosh Raeen
Kourosh Raeen
23,733 Points

The return type of the method getAllAuthors() should be Set<String>. In the for loop, post should be of type BlogPost. And finally, to add each author to the TreeSet use the add() method:

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> results = new TreeSet<String>();
    for(BlogPost post : mPosts){
      results.add(post.getAuthor());
    }
    return results;
  }
}
Shane May
Shane May
5,114 Points
Shane May
Shane May
5,114 Points

Thank you very much. I completely forgot to set the initial return statement to Set, and of course use BlogPost in the for loop. Thank you again for your help.