Hi, I have casted the obj to string obj but also I'm getting the error.pls, help.

Question

I have casted the obj but also i'm getting this error.

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 = "";
    BlogPost bg = new BlogPost("Udaya","Java","DataStructure","Tech",new java.util.Date(System.currentTimeMillis()));
    if(obj instanceof String){
    result = (String) obj;
    }
    if(obj instanceof BlogPost){
      result = (String) obj;
    }
  return result;  
  }

}

Answer 1 · 2018-01-26T15:07:30Z

January 26, 2018 3:07pm

Hi there,

The first task requires you to return the obj cast as a String if it is a String. You've done that fine:

if(obj instanceof String){
  return (String) obj;
}

(you can set result to this string and return that, if you like, as you did.

The instructions to this challenge state that The method getTitleFromObject will be called and passed a String and/or a com.example.BlogPost, so there are only two data types that the method will receive. We've handled how to manage the program flow if a String is passed in. Now we need to work on the other option; what happens when a BlogPost is passed in. Remember, the method must return a String; that's what the method signature states.

So, in the else clause of the if statement used above , we need to cast obj to a BlogPost and then call the getTitle() method on it. That gives us the title of the BlogPost (a String) which we need to return. That can all look like this, but you may want to assign this string into result and return that - up to you!

This is fewer lines of code:

    if(obj instanceof String){
      return (String) obj;
    } else {
      return ((BlogPost) obj).getTitle();
    }

but maybe this is clearer? Personal preference, I reckon:

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

I hope that makes sense.

Steve.

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Udayakumar T

Udayakumar T

Hi, I have casted the obj to string obj but also I'm getting the error.pls, help.

1 Answer

Steve Hunter

Steve Hunter