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Java Java Data Structures Getting There Type Casting

Alexander Lebedev
Alexander Lebedev
5,875 Points

java.lang.ClassCastException: com.example.BlogPost cannot be cast to java.lang.String

I'm stuck on the second part of the final challenge. What am I doing wrong?

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 Object) {
      result = (String) obj; 
    }

    else if (obj instanceof BlogPost) {
        BlogPost post = (BlogPost) obj;
        result = post.getTitle();
    }


    return result;
  }
}

2 Answers

andren
andren
28,558 Points

The issue is the condition of your first if statement:

if (obj instanceof Object) {
    result = (String) obj; 
}

You are meant to check if obj is a String, but you are actually checking if it is an Object, which will always be true because all objects in Java is an instance of the Object class. I assume this is some kind of typo since you do the proper check with the BlogPost object.

Anyway if you just change it to this:

if (obj instanceof String) {
    result = (String) obj; 
}

Then you will pass the challenge.

Alexander Lebedev
Alexander Lebedev
5,875 Points

Thank you andren! It worked :)