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Java Java Data Structures - Retired Organizing Data Comparable

Ignacio Martinez de Salinas
Ignacio Martinez de Salinas
1,389 Points

Do I need a Array to order the dates?

The question demands ordering the dates, do I have to define an array so I can order all the BlogPost? I think I dont understand correctly the question.

com/example/BlogPost.java
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;
  }
  @Override
  public int compareTo(Object obj){
    com.example.BlogPost another = (com.example.BlogPost) obj;
    if(equals(another)){
      return 0;
    }

    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;
  }
}

2 Answers

Kourosh Raeen
Kourosh Raeen
23,733 Points

In task 3 you need to modify the campareTo() method so that the comparison is done based on mCeartionDate. To to that we can delegate the job to the Date classes compareTo() method:

@Override
  public int compareTo(Object obj) {
    if(mCreationDate.compareTo(((BlogPost) obj).mCreationDate) < 0) {
      return -1; 
    } else if(mCreationDate.compareTo(((BlogPost) obj).mCreationDate) == 0) {
      return 0;
    }
    return 1;
  }
Kourosh Raeen
Kourosh Raeen
23,733 Points

No. You need to have the class implement the Comparable interface and override the compareTo() method. The code in Task 1 will look like this:

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 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;
  }

  @Override
  public int compareTo(Object obj) {
    return 1;
  }
}
Ignacio Martinez de Salinas
Ignacio Martinez de Salinas
1,389 Points

Yes! but in the task 3 when it says to order the blogpost's creation date? How I do that? I compare the dates but how I get them in the good order?

Kourosh Raeen
Kourosh Raeen
23,733 Points

Hi Ignacio! See my answer below.