Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

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

Getting lots of errors

./com/example/Blog.java:5: error: expected import.java.util.TreeSet; ^ ./com/example/Blog.java:13: error: illegal start of expression Set set = TreeSet<>(); ^ ./com/example/Blog.java:13: error: -> expected Set set = TreeSet<>(); ^ ./com/example/Blog.java:13: error: ';' expected Set set = TreeSet<>(); ^ ./com/example/Blog.java:15: error: ')' expected for(BlogPost authorName: mPosts){ ^ ./com/example/Blog.java:15: error: not a statement for(BlogPost authorName: mPosts){ ^ ./com/example/Blog.java:15: error: ';' expected for(BlogPost authorName: mPosts){ ^ ./com/example/Blog.java:5: error: package .java.util does not exist import.java.util.TreeSet; ^ ./com/example/Blog.java:11: error: cannot find symbol public set getAllAuthors(){ ^ symbol: class set location: class Blog ./com/example/Blog.java:13: error: cannot find symbol Set set = TreeSet<>(); ^ symbol: variable TreeSet location: class Blog ./com/example/Blog.java:13: error: lambda expression not expected here Set set = TreeSet<>(); ^ ./com/example/Blog.java:17: error: cannot find symbol set.add(authorName.getAuthor()); ^ symbol: variable authorName location: class Blog Note: JavaTester.java uses unchecked or unsafe operations. Note: Recompile with -Xlint:unchecked for details. 12 errors

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 set<String> getAllAuthors(){

  Set<String> set = TreeSet<>();

    for(BlogPost authorName: mPosts){

    set.add(authorName.getAuthor());

    }

  return set;
 }

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

  public List<BlogPost> getPosts() {
    return mPosts;
  }
}
Simon Coates
Simon Coates
28,694 Points

there's an unexpected dot on one of your imports.

the method signature has set<String> instead of Set<String>

treeset instantiation is weird.

1 Answer

Simon Coates
Simon Coates
28,694 Points

the following seems to work:

package com.example;

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

public class Blog {
  List<BlogPost> mPosts;

 public Set<String> getAllAuthors(){

  Set<String> set = new TreeSet<String>();

    for(BlogPost authorName: mPosts){

    set.add(authorName.getAuthor());

    }

  return set;
 }

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

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