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Java Java Data Structures Organizing Data Comparable

Tim Strand
Tim Strand
22,458 Points

i dont understand what challenge 3/3 is asking for. I have added a sort which doesnt work i keep getting compiler errors

a couple issues: 1) compiler errors on my Arrays.sort even though it matches what we used in class 2) not sure what its wanting when getting error Expected -1 but got 1

i had assumed this challenge had to do with sorts since it says lets order the blog posts by creation date.

package com.example;
import java.util.Arrays;
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) {
   BlogPost other = (BlogPost) obj;
    if (equals(other)) {
     return 0; 
    int dateCmp = mCreationDate.compareTo(other.mCreationDate);
    if (dateCmp ==0) {
     return mTitle.compareTo(other.mTitle); 
    return 1;

  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;

 BlogPost[] blogDates = new BlogPost[10];


1 Answer

Grigorij Schleifer
Grigorij Schleifer
10,365 Points

Hi Tim,

  public int compareTo(Object obj) {
   BlogPost other = (BlogPost) obj;
    if (equals(other)) {
// if your BlogPost is equal to another BlogPost (accepted as parameter)
// return 0
     return 0; 
   return mCreationDate.compareTo(other.mCreationDate);
// no need to create an extra integer or if loop
// mCreationDate is the basis of our comparison
// on this basis you call the compareTo method and give that method the creation date of the parameter obj 
// casted as BlogPost to be compared and sorted 
// Java automaticly sort the dates for you

I am not sure, but if the creation date of your BlogPost is younger, then the returned value will be -1. In the opposite case > 0.

The returned integer helps the col´mpiler to sort the creation dates chronologically ...

I hope that makes sense :)