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

Steven Morimoto
PLUS
Steven Morimoto
Courses Plus Student 1,836 Points
Posted by Steven Morimoto
Steven Morimoto
Courses Plus Student 1,836 Points

I can't figure out the Sets quiz

Hi,

I've been working on this one question for the past 2 and a half days. I'm really at a loss as to how to solve this problem and I would greatly appreciate the assistance. I suspect there is something wrong with the above lists being assigned the generic BlogPost which makes it incompatible with a String, but I've been stuck on trying to work around that problem with all the leads that I've come up with being exhausted. To put it in a single phrase, how do I solve this?

Thanks in advance,

Steve

PS. Why does the compiler keep saying that my for statement requires a ; at the end when I know that it does not? What exactly is the compiler saying is wrong?

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.ArrayList;
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 List<String> getAllAuthors()
  {
    List<String> names = new ArrayList<String>();
    for(String authorNames = getPosts())
    {
      names.add(authorNames);
    }
    Set<String> set = new TreeSet<String>(names);
    return names;
  }
}

1 Answer

Timothy Hilley
Timothy Hilley
2,292 Points 
package com.example;
import com.example.BlogPost;                           //dont forget your import!!! its important!!! :D

import java.util.List;
import java.util.Set;
import java.util.TreeSet;

public class Blog {
  List<BlogPost> mPosts;
  TreeSet<String> authors = new TreeSet<>();

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

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

  public Set<String> getAllAuthors() { //the requested method
    for (BlogPost post : mPosts) {          //the loop (for each post in the list mPosts...
    authors.add(post.getAuthor());        //add that posts other to my list of String Authors :D
    }
    return authors;                                   //return my alphabitised none duplicate list 

  }
}