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Java Java Data Structures Exploring the Java Collection Framework Maps

Hash Map 6

Sorry to be such a pain here, but this code still does not compile. The compiler is complaining about this:

./com/example/Blog.java:20: error: cannot find symbol
    Map hashCounts = new HashMap<>();
    ^
  symbol:   class Map
  location: class Blog
Note: JavaTester.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details

```java

I believe i've created the hash map properly, as to Craig Dennis' instructions, but I have not had this work successfully yet.

Can you guys help?

```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 java.util.HashMap;

public class Blog {
  List<BlogPost> mPosts;

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

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

  public HashMap<String,Integer> getCategoryCounts() {
    Map<String,Integer> hashCounts = new HashMap<>();
    Integer count = 0;
    for (BlogPost post : mPosts) {
            String author = post.getAuthor();
                        if (hashCounts.get(author) == null) {
                 count = 0;
            }
                else {
                count++;
            }
                    hashCounts.put(author,count);               
    }

        return hashCounts;
  }

}

1 Answer

Kabir Gandhiok
Kabir Gandhiok
12,553 Points

The compiler cannot find Map. You have imported HashMap but you also need to import Map.