Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

Java Java Data Structures - Retired Getting There Type Casting

Sean Flanagan
Sean Flanagan
33,235 Points

Typecasting Challenge Task 2

Hi. I'm stuck on this one.

Here's my code:

import com.example.BlogPost;

public class TypeCastChecker {
  /***************
  I have provided 2 hints for this challenge.
  Change `false` to `true` in one line below, then click the "Check work" button to see the hint.
  NOTE: You must set all the hints to false to complete the exercise.
  ****************/
  public static boolean HINT_1_ENABLED = false;
  public static boolean HINT_2_ENABLED = true;

  public static String getTitleFromObject(Object obj) {
    // Fix this result variable to be the correct string.
    if (obj instanceof com.example.BlogPost) {
      return (getTitle) result;
    }

    if (obj instanceof BlogPost) {
      BlogPost post = (BlogPost) obj;
      return result = (String) post.getTitle();
    }
    return result;
  }
}

I'd be grateful for any help. :-)

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 getAuthor() {
      return mAuthor;
    }

    public String getTitle() {
      return mTitle;
    }

    public String getBody() {
      return mBody;
    }

    public String getCategory() {
      return mCategory;
    }

    public Date getCreationDate() {
      return mCreationDate;
    }
}
TypeCastChecker.java
import com.example.BlogPost;

public class TypeCastChecker {
  /***************
  I have provided 2 hints for this challenge.
  Change `false` to `true` in one line below, then click the "Check work" button to see the hint.
  NOTE: You must set all the hints to false to complete the exercise.
  ****************/
  public static boolean HINT_1_ENABLED = false;
  public static boolean HINT_2_ENABLED = true;

  public static String getTitleFromObject(Object obj) {
    // Fix this result variable to be the correct string.
    if (obj instanceof com.example.BlogPost) {
      return (getTitle) result;
    }

    if (obj instanceof BlogPost) {
      BlogPost post = (BlogPost) obj;
      return result = (String) post.getTitle();
    }
    return result;
  }
}

2 Answers

Jon Kussmann
PLUS
Jon Kussmann
Courses Plus Student 7,254 Points

Hi Sean,

What sort of error are you getting? I personally solved part two like so:

if (obj instanceof BlogPost) {
return ((BlogPost)obj).getTitle();
}

If you want it spread out a little more:

if (obj instanceof BlogPost) {
  BlogPost post = (BlogPost)obj;
  return post.getTitle();
}
Sean Flanagan
Sean Flanagan
33,235 Points

Hi Jon. Your code was a big help. Thanks again. :-)

Hi Jon,

Your comment was exactly the help I needed. Can you explain the syntax behind ((BlogPost)).getTitle();?

I tried BlogPost obj.getTitle() and got a compiler error because it thought I was casting the result of getTitle as BlogPost. How did you know adding the parenthesis would work and was required?

Thanks!

Aditya Puri
Aditya Puri
1,080 Points

Jon 2 questions-

1) Why do we have 2 extra () around the line (BlogPost)obj ? Can't we just do return ((BlogPost)obj).getTitle();

2) When do we use these type conversions?

Rob B
Rob B
11,677 Points

Thanks for the help. I've had to check everything in this course since the beginning because the instructions have always been missing something, or has been too vague on something.

Thanks again for the help.