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Java Java Data Structures Exploring the Java Collection Framework Sets

Johannes Pedersen
Johannes Pedersen
1,006 Points

non-static method getAuthor() cannot be referenced from a static context

I keep getting this error, can anyone help me out please?

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.TreeSet;
import java.util.Set;

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> allAuthors = new TreeSet<>();
    for(BlogPost author : getPosts()){
     allAuthors.add(BlogPost.getAuthor());

    }
    return allAuthors;
  }
}

1 Answer

andren
andren
28,520 Points

The issue is that you try to call the getAuthor method directly from the BlogPost class, rather than calling it from author which is the variable that holds the BlogPost objects that the for loop is pulling out.

If you change BlogPost.getAuthor() to author.getAuthor() like this:

public Set<String> getAllAuthors(){
  Set<String> allAuthors = new TreeSet<>();
  for(BlogPost author : getPosts()){
    allAuthors.add(author.getAuthor());

  }
  return allAuthors;
}

Then your code will work.