Welcome to the Treehouse Community

The Treehouse Community is a meeting place for developers, designers, and programmers of all backgrounds and skill levels to get support. Collaborate here on code errors or bugs that you need feedback on, or asking for an extra set of eyes on your latest project. Join thousands of Treehouse students and alumni in the community today. (Note: Only Treehouse students can comment or ask questions, but non-students are welcome to browse our conversations.)

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and a supportive community. Start your free trial today.

Java Java Data Structures Getting There Type Casting

I don't understand what the exercise wants me to do.

I have no idea what this exercise is about. What am I supposed to do?

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;
import java.util.Date;

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){
    result = (String) obj;
    }


    return result;
  }
    if (BlogPost instanceof obj){
    Date date = new Date();
    BlogPost blog = new BlogPost("ana","maria","maria","maria",date);
    getTitle(blog);
    }
}

2 Answers

Justin Horner
STAFF
Justin Horner
Treehouse Guest Teacher

Hello Chelaru,

You're doing well! You don't need to create a new instance of a BlogPost in the getTitleFromObject method because the object being passed it will be either a String or a BlogPost instance.

To be explicit, we can use an if/else statement with instanceof, like this:

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

If the else condition is true, then we know obj is a BlogPost instance be passing to us as the obj argument, we just need to get the title from the instance. You can look at the BlogPost.java file to see what methods are provided. In this case, we simply call getTitle().

Since the result variable is already being returned, all we need to do is set its value. Be sure to leave the return statement at the bottom so that result is being returned.

I hope this helps.

Thx! It worked.