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

Daniel Paradiso
PLUS
Daniel Paradiso
Courses Plus Student 3,915 Points
Posted by Daniel Paradiso
Daniel Paradiso
Courses Plus Student 3,915 Points

I cannot get the return of getTitle() after seeing whether obj is an instance of BlogPost

I have flipped all the options around to do what I think it should do, I have added BlogPost blogPost = (BlogPost) obj; and I get java.lang.ClassCastException. I have been at this for almost 2 hours. Please 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 = false;

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

2 Answers

Jeremy Hill
Jeremy Hill
29,567 Points
Jeremy Hill
Jeremy Hill
29,567 Points

Your method should look like this:

 public static String getTitleFromObject(Object obj) {
    // Fix this result variable to be the correct string.
    String result = "";

    if(obj instanceof String)
      result = (String)obj;

    if(obj instanceof BlogPost){
       BlogPost bp = (BlogPost)obj;
      result = bp.getTitle();
    }

    return result;
  }