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Java Java Data Structures Getting There Type Casting

Lucian Vrabiescu
Lucian Vrabiescu
735 Points
Posted by Lucian Vrabiescu
Lucian Vrabiescu
735 Points

Why doesen't it work?

I get some weird compiler errors.

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 = true;
  public static boolean HINT_2_ENABLED = true;

  public static String getTitleFromObject(Object obj) {
    if (obj instanceOf String){
      String result = (String) obj;
    }
    return result;
  }
}

1 Answer

andren
andren
28,558 Points
andren
andren
28,558 Points

There are two issues:

  1. The instanceof keyword should be typed all in lowercase, not in camelCase.

  2. You define the result variable within the if statement, due to the way variable scope works in Java that variable will only be accessible within the if statement, not outside it.

If you fix the spelling of instanceof and declare the result variable outside the if statement then your code will work. You will also need to disable the challenge hints you have enabled though, in order to continue to the next task.

Like this:

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; // Turn off hint
  public static boolean HINT_2_ENABLED = false; // Turn off hint

  public static String getTitleFromObject(Object obj) {
    String result = ""; // Declare and initalize the result variable
    if (obj instanceof String){ // Use instanceof to check if obj is a String
      result = (String) obj; // Set existing result variable equal to obj cast as String
    }
    return result; // Return result variable
  }
}