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Java Java Data Structures - Retired Getting There Type Casting

Grigorij Schleifer
Grigorij Schleifer
10,365 Points
Posted by Grigorij Schleifer
Grigorij Schleifer
10,365 Points

Need help

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 = "This ist a String or a BlogPost";
    BlogPost myBlogPost;

    if(result instanceof Object){
     result = (String) obj;
     return result; 
    }else if(BlogPost instanceof Object){
     myBlogPost = (BlogPost) obj;
     return myBlogPost.getTitle();
    }
     return "";
  }
}

The error says that i didnt initialised the BlogPost? What i am doing wrong?

2 Answers

Victor Learned
Victor Learned
6,976 Points
Victor Learned
Victor Learned
6,976 Points

Your if statement is attempting to use the variable before it's been given a value or initialized. You only declared a BlogPost variable. You never actually initialized. Before a variable can be used it must be given an initial value. This is called initializing the variable. If we try to use a variable without first giving it a value:

Example:

int numberOfDays; //try and add 10 to the value of numberOfDays 
numberOfDays = numberOfDays + 10;

the compiler will throw an error

You actually don't even need to create a variable to since what you really want is just the title. So you can just cast the obj to a BlogPost and immediately call the getTitle method which returns the string you want:

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

    if(result instanceof Object){
     result = (String) obj;
    }else if(BlogPost instanceof Object){
     result = ((BlogPost) obj).getTitle();
    }
     return result;
  }
Grigorij Schleifer
Grigorij Schleifer
10,365 Points
Grigorij Schleifer
Grigorij Schleifer
10,365 Points

I added 

BlogPost myBlogPost = new BlogPost();

And i get this error :

./TypeCastChecker.java:15: error: constructor BlogPost in class BlogPost cannot be applied to given types; BlogPost blogPost = new BlogPost(); ^ required: String,String,String,String,Date found: no arguments reason: actual and formal argument lists differ in length 1 error

Victor Learned
Victor Learned
6,976 Points
Victor Learned
Victor Learned
6,976 Points

That was my fault for not actually looking at the code before suggesting an answer. I've updated my answer and I have tested to ensure it's correct.