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Java Java Data Structures Organizing Data Comparable

Can not figure this out at all. Please help.

Challenge Task 1 of 3 Comparable

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

import java.util.Date;

public class BlogPost {
  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;
  }
}

2 Answers

Grigorij Schleifer
Grigorij Schleifer
10,365 Points

Hi djwyatt,

allow me to comment the challenge:

package com.example;

import java.util.Date;

// TASK 1
public class BlogPost implements Comparable {
  // implement the Comparable interface

  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;
  }

  // TASK 2
  @Override
  public int compareTo(Object obj) {
// creating a method, that returns an integer and accepts an Object as parameter

    BlogPost post = (BlogPost) obj;
    // Here you cast the parameter "obj" into a BlogPost Object. 

    if(equals(post)) {
     // equals is referring to the BlogPost you are inside
     // and "post" is representing the Object that was casted to BlogPost above
     // so "equals(post)" says: if the object that is castet to BlogPost is equals to BlogPost you are inside
     // return 0
   return 0;
    }
   return 1;
// if they are not the same, return 1
  }

}

For the Task 3 you will replace the last return statement with the comparation prozess and return the result (0 or 1)

 mCreationDate.compareTo(post.mCreationDate);
// this line is ordering the creation dates chronologicaly 
// the oldest go first :)
// mCreationDate is a Date of the BlogPost you are inside
// post.mCreationDate gets you the creation date of the BlogPost that you are comparing with to mCreationDate
// if they are not equal, the returned result will be 1

The if statement is ensuring that the BlogPost is not compared to itself.

Does it make sense?

Grigorij

Yes it makes sense, and thank you for the help Grigorji!