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Java Java Data Structures - Retired Getting There Type Casting

michael figueroa
michael figueroa
5,680 Points

type casting and importing packages.

i am trying to type cast obj and use the getTitle() method to assign the title String to result. however i keep getting an error that says the method cannot be found even thought the package for the BlogPost class has been important. Is there anything wrong with the code? or is there a bug in the program?

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

1 Answer

Kourosh Raeen
Kourosh Raeen
23,733 Points

You need an extra set of parenthesis to ensure that casting happens before you call the getTitle() method:

result = ((BlogPost)obj).getTitle();
michael figueroa
michael figueroa
5,680 Points

Ohhh i see. So because obj is of type Object then it doesnt have the getTitle() method and that's why i kept getting the method not found error. So you have ensure explicitly that the type casting takes place before anything else happens. this helps a lot thank you!!!!

Kourosh Raeen
Kourosh Raeen
23,733 Points

That's correct. Glad I could help!

Jonathan Grieve
Jonathan Grieve
Treehouse Moderator 91,253 Points

If you want to make sure you can count down you can use the instanceof keyword. Here's an example of this in the docs.

if (obj instanceof MountainBike) {
  MountainBike myBike = (MountainBike)obj;
}

https://docs.oracle.com/javase/tutorial/java/IandI/subclasses.html.