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 Getting There Type Casting

Posted by RUCHI MISHRA
RUCHI MISHRA
2,968 Points

No understanding question

Not understanding what the requirement is?!

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 getTitleFromObject (Object obj)
  {
    obj =  mTitle;

   return (String)obj;
  }
    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 = "";
    return result;
  }
}

1 Answer

michaelcodes
michaelcodes
5,604 Points
michaelcodes
michaelcodes
5,604 Points

Hi there! So for this problem we are going to be using this method inside TypeCastChecker.java, not BlogPost.java The method is already roughly setup with:

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

What the first part of the problem is asking is for us to return whatever object is passed to us, but to correctly check if it a String (rather than a BlogPost.) We can accomplish this by using the instanceof keyword to check if the object passed into the method is an instance of string. This will give us true or false, so we put it inside an if statement. 

    if(obj instanceof String) { //(obj instanceof String) will return true or false

If it is of type String, we will typecast the object into a String, and store it in our result variable:

    result = (String) obj;

When we put all of this together into the method we get:

  public static String getTitleFromObject(Object obj) {
    String result = "";
    if(obj instanceof String) {//If the object is a string then we:
    result = (String) obj;    //Typecast that object as a String, and store in result
    }
    return result; //Finally we return that result 
  }
}

Hope this helps! if you have any questions about part 2 and handling the BlogPost let me know.

Take care and happy coding :)

RUCHI MISHRA
RUCHI MISHRA
2,968 Points

Thanks for help