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Java Java Data Structures - Retired Exploring the Java Collection Framework Upgrade Comparable to use Generics

Sean Flanagan
Sean Flanagan
33,235 Points

Upgrade Comparable to Use Generics

Hi. I've tried this one but I'm stuck. Thanks in advance for any help. :-)

com/example/BlogPost.java
package com.example;

import java.io.Serializable;
import java.util.Date;

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 obj) {
    BlogPost other = (BlogPost) obj;
    if (equals(other)) {
      return 0;
    }
    return mCreationDate.compareTo(BlogPost.mCreationDate);
  }

  public String[] getWords() {
    return mBody.split("[^\\w']+");
  }

  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;
  }
}

1 Answer

Enrique Munguía
Enrique Munguía
14,311 Points

Your code must compare the this instance and the instance received in compareTo method. You don't have to cast obj to BlogPost because it is already a BlogPost. The code may look like this:

public int compareTo(BlogPost obj) {
    if (this.equals(obj)) {
      return 0;
    }
    return this.mCreationDate.compareTo(obj.mCreationDate);
  }
Sean Flanagan
Sean Flanagan
33,235 Points

Hi. I tried your code and it worked. Thanks. :-)