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Java Java Data Structures Organizing Data Comparable

This section of the course is really confusing. I don't understand, thus, can't solve this task.

I'm stuck at this last task and have no idea why it isn't working.

package com.example;

import java.util.Date;

public class BlogPost implements Comparable {
  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(Object obj) {
    Object other = (BlogPost) obj;
    if(equals(other)) {
      return 0;
    return mCreationDate.compareTo(other.mCreationDate);

  public String[] getWords() {
    return mBody.split("\\s+");

  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

28,558 Points

The issue is the line where you cast the obj:

Object other = (BlogPost) obj;

You cast obj correctly but you assign it to a variable of type Object, which causes it to be automatically cast as an Object again.

The point of casting something is that it returns the object as the type you specify. The line should look like this:

BlogPost other = (BlogPost) obj;

That will create a BlogPost object that contains obj cast as a BlogPost.

That is the only issue in your solution. So once you correct that line you should be able to pass.