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Java Java Data Structures Exploring the Java Collection Framework Sets

Gonzalo Torres del Fierro
PLUS
Gonzalo Torres del Fierro
Courses Plus Student 16,750 Points

Set Challenge

hello, i was reading the forum coments, and serching for my self, but i can not go throw this unique_error, that is telling me this;

./com/example/Blog.java:18: error: cannot find symbol for (BlogPosts authorName : mPosts) { ^ symbol: class BlogPosts location: class Blog Note: JavaTester.java uses unchecked or unsafe operations. Note: Recompile with -Xlint:unchecked for details. 1 error

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;
import com.example.BlogPost;


public class Blog {
  List<BlogPost> mPosts;

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

 public Set <String> getAllAuthors(){
   Set<String> set = new TreeSet<String>();
   for (BlogPosts authorName : mPosts) { 
     set.add(authorName.getAuthor());
   }
   return set;
 }
  public List<BlogPost> getPosts() {
    return mPosts;
  }
}

2 Answers

Gonzalo Torres del Fierro
PLUS
Gonzalo Torres del Fierro
Courses Plus Student 16,750 Points

hello, i found finally, the error, was related with this:

1-. first, i had to import the proper interface to my programming place , and here we have what was necessary to do it; package com.example;

import java.util.List; import java.util.Set; import java.util.TreeSet; import java.util.HashSet; import com.example.BlogPost;

2-. then, i realize, that it was an extra "S" on my Code, and i just deleted... ( see below ,for (BlogPosts.../ must say "BlogPost")

public Set <String> getAllAuthors(){ Set<String> set = new TreeSet<String>(); for (BlogPosts authorName : mPosts) { set.add(authorName.getAuthor()); }

and with this two litle changes, everything was running ok...

There probably shouldn't be a space between: "Set" and <String> in you method heading. This is what I did to pass the challenge:

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> authors = new TreeSet<>();

    for(BlogPost post : mPosts){
     authors.add(post.getAuthor()); 
    }
    return authors;
  }
}
Gonzalo Torres del Fierro
Gonzalo Torres del Fierro
Courses Plus Student 16,750 Points

Jeremy, thank you , for your answer, and i´m glad to have persons like you that really help on this task of learning code...