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

Eric Shelby
Eric Shelby
28,300 Points
Posted by Eric Shelby
Eric Shelby
28,300 Points

Type Casting problems

I'm having trouble understand this question. "The method getTitleFromObject will be called and passed a String and/or a com.example.BlogPost. For this first task, return the object obj type casted as a String if it is in fact a String." Does it simply want me to somehow add obj to the result variable and return that? Does it want me to use a method from BlogPost.java? I have no idea what I'm doing.

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 (obj instanceof String == true) {
      obj = result;
    }
    return result;
  }
}

2 Answers

Peter Furler
Peter Furler
31,647 Points
Peter Furler
Peter Furler
31,647 Points

You are nearly correct except for your condition and also inside the if statement of the getTitleFromObject method you have not typecast obj as a string and not assign it to result.

This will make result's type a String, which will then be returned as a string as the method requires. Here is my fix:

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

Keep all other code the same.

Unsubscribed User
Unsubscribed User
1,321 Points 
if(obj instanceof String) {
    result = (String) obj;
}

Just wanted to add the code formatted.

Eric Shelby
Eric Shelby
28,300 Points
Eric Shelby
Eric Shelby
28,300 Points

Thanks for your answer. It cleared things up.