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Java Java Data Structures Exploring the Java Collection Framework Sets

Ronit Mankad
Ronit Mankad
12,166 Points
Posted by Ronit Mankad
Ronit Mankad
12,166 Points

Logical Error

I'm not able to logically understand it. I'm not able to understand what to write in the for loop. Please Help. Thanks in Advance.

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;
  }

  public Set<BlogPost> getAllAuthors() {
   Set<String> result = new TreeSet<String>();
   for(Blog blog : BlogPost ) {
   result.addAll(blog.getPosts());
   }
   return result;
  }
}

1 Answer

jcorum
jcorum
71,830 Points

Ronit, you want the authors.

  public Set<String> getAllAuthors() {
    Set<String> authors = new TreeSet<>();
    for (BlogPost p : mPosts) {
      authors.add(p.getAuthor());
    }
    return authors;
  }

So it's a good idea to call the output authors. Then you need to loop through the posts in mPosts, grab each author, and add him or her to the set.