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Java Java Data Structures Exploring the Java Collection Framework Sets

Jay Bhatt
Jay Bhatt
6,502 Points
Posted by Jay Bhatt
Jay Bhatt
6,502 Points

How do I retrieve the authors (using getAuthors()) from the original BlogPost class into the Blog class?

I am having trouble using the getAuthors() to get the authors. Please help

com/example/BlogPost.java 
package com.example;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import java.util.Set;
import java.util.TreeSet;
import java.util.HashSet;


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;
import java.util.HashSet;

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> ();
    BlogPost
    for (BlogPost post: mPosts[0]) {
      authors.addAll(post.getAuthor());
    }
    return authors;

  }
}

1 Answer

Alexander Nikiforov
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.a{fill-rule:evenodd;}techdegree seal-36
Alexander Nikiforov
Java Web Development Techdegree Graduate 22,175 Points
Alexander Nikiforov
.a{fill-rule:evenodd;}techdegree seal-36
Alexander Nikiforov
Java Web Development Techdegree Graduate 22,175 Points

You are almost there. Here is hint sudo code:

  public Set<String> getAllAuthors() {
    // this is correct : initialized new TreeSet
    Set<String> authors = new TreeSet<String> ();
    // BlogPost  wrong 

    // Cycle through ALL mPosts, 
    // not through mPosts[0], which is only one Post at index 0
    // for (BlogPost post: mPosts[0]) {  // FIX HERE and uncomment

    // Hint: use `add` method not `addAll`, because you are inside loop
    // you are looping for each post
    // and for each post you add one author
    // authors.addAll(post.getAuthor());  // FIX HERE and uncomment
    //}

    // that is correct line
    return authors;

  }
Jay Bhatt
Jay Bhatt
6,502 Points
Jay Bhatt
Jay Bhatt
6,502 Points

It worked. Thank you. I don't why I did addAll or mPost[0].