What's needed here?

Question

I'll attach my code:

package com.example;

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

public class BlogPost implements Comparable, 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;
  }

  @Override public int compareTo(BlogPost other) {
    if (equals(other)) {
      return 0;
    }
    return mCreationDate.compareTo(other.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;
  }
}

com/example/BlogPost.java

package com.example;

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

public class BlogPost implements Comparable, 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;
  }

  @Override public int compareTo(BlogPost other) {
    if (equals(other)) {
      return 0;
    }
    return mCreationDate.compareTo(other.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;
  }
}

Answer 1 · 2016-01-11T23:24:02Z

January 11, 2016 11:24pm

Casey;

Let's have a look:

Task 1

Now that we know about Generics, let's upgrade our Comparable interface defined on the BlogPost class to use it. Remember to change the parameter in the compareTo method to be of type BlogPost.

I'm going to work backwards here a bit and hopefully by the end you will see why. Our given compareTo() method is:

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

We're asked to "upgrade" this to use a BlogPost instead of an Object here and in doing so remove the casting statement inside our method.

step1.java

  public int compareTo(BlogPost other) {
    if (equals(other)) {
      return 0;
    }
    return mCreationDate.compareTo(other.mCreationDate);
  }

Great. Almost there. If we run that code, we get back an error:

BlogPost is not abstract and does not override abstract method compareTo(Object) in Comparable

Great. What does that mean? Well, if we think for a second, during our upgrade process we forgot to "upgrade" our class interface in addition to our code. We need to let our class know that we want to utilize Comparable<BlogPost> to be able to compare BlogPost objects. Therefore we need to add that up top where we define our class:

snippet.java

public class BlogPost implements Comparable<BlogPost>, Serializable {
// other stuff here

Take a look at the Comparable documentation for more information.

Post back if you are still stuck or have further questions.

Happy coding,
Ken

Answer 2 · 2016-01-12T22:55:37Z

January 12, 2016 10:55pm

I got it Ken, thanks!

Answer 3 · 2016-02-06T20:49:26Z

February 6, 2016 8:49pm

Thank you Ken, I didn't realize I had to change my generic in the call to compareTo and was starting to bang my head against the monitor. I go through so many monitors that way.

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Casey Huckel

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What's needed here?

3 Answers

Ken Alger

Ken Alger

Task 1

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Casey Huckel

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