Cannot find symbol

Question

I'm getting errors: ./TypeCastChecker.java:18: error: cannot find symbol result = (BlogPost)obj.getTitle; ^ symbol: variable getTitle location: variable obj of type Object ./TypeCastChecker.java:18: error: incompatible types: BlogPost cannot be converted to String result = (BlogPost)obj.getTitle; ^ 2 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 = 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;
    } else if(obj instanceof com.example.BlogPost) {
      result = (BlogPost)obj.getTitle;
    }
    return result;
  }
}

Answer 1 · 2017-04-30T19:07:02Z

April 30, 2017 7:07pm

Hi Binyamin,

First of all you missed the set of parenthesis after

(BlogPost)obj.getTitle;

So it should be:

(BlogPost)obj.getTitle();

Also, you need a more specific cast. What you wanted is convert the obj variable to BlogPost however is not doing that. It's converting what obj.getTitle() returns to BlogPost instead, that is why it shows the error "BlogPost cannot be converted to String", because you are trying to assign to the result String variable something converted to BlogPost.

To fix that, you need to use another set of parenthesis around the casting and the variable you want to convert like this:

((BlogPost)obj).getTitle();

In this way it first converts the obj variable to BlogPost and then it calls the method and returns the title String.

Answer 2 · 2017-04-30T19:12:18Z

April 30, 2017 7:12pm

The first if is correct. But there are a couple problems in your else if block.

Instead of checking if the object is an instance of com.example.BlogPost, you want to do:

else if (obj instanceof BlogPost) {

}

In this block you're calling the getTitle method on the post, but that method will only work on a certain type. So first you need to cast the obj as a BlogPost, then you can call the getTitle method on it.

So one way you can do that is to create a new variable to store the obj of type BlogPost, then set result equal to that object with getTitle called on it.

Example:

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

Welcome to the Treehouse Community

Looking to learn something new?

Binyamin Friedman

Binyamin Friedman

Cannot find symbol

2 Answers

Leandro Botella Penalva

Leandro Botella Penalva

dmzstudio45

dmzstudio45