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Java Java Data Structures - Retired Getting There Type Casting

Shane May
Shane May
5,114 Points
Posted by Shane May
Shane May
5,114 Points

Casting variable in java and I have no clue what I am doing, please help!

I am on the last challenge in the first set of Java Data Structure. We just watched a video about down/up casting, however I have no idea what the challenge is asking me to do OR how to do it. Could some one help clear this up for me? (Instructions) 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.

I've included BlogPost.java for your reference only.

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 = true;

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

1 Answer

Clayton Perszyk
MOD
Clayton Perszyk
Treehouse Moderator 48,850 Points
Clayton Perszyk
Clayton Perszyk
Treehouse Moderator 48,850 Points

Hey Shane,

You want to use a conditional statement (i.e. if (condition) { run code }); in the condition, you want to check if the object, obj, is a string (you will use instanceof for this and it will return true or false depending on the object's type). Within the body of the conditional statement, you want to cast the object to a string (i.e. (String) obj) and then assign it to the result variable. Also, make sure to set the hints to false when you don't need them, or the challenge wont pass, regardless of whether the code is correct or not. Additionally, you don't need to modify the existing code; just put your conditional check with type casting between the String result variable declaration and the return statement.

Best,

Clayton