SOS on Java Type Casting

Question

Prompt: Now make sure that if a com.example.BlogPost is passed in for obj that you then cast it to a BlogPost. Return the results of the getTitle method on the newly type-casted BlogPost instance.

I've included BlogPost.java for your reference only

Why u no work? Am I supposed to put in com.example.BlogPost after instanceof?

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

    if (obj instanceof com.example.BlogPost) {
      result = (BlogPost) obj;
    }

    return result;
  }
}

Answer 1 · 2016-10-03T19:02:54Z

October 3, 2016 7:02pm

Please read the task 2 once again:

Now make sure that if a com.example.BlogPost is passed in for obj that you then cast it to a BlogPost. Return the results of the getTitle method on the newly type-casted BlogPost instance

Take a look at the last sentence: you haven't use getTitle method on the BlogPost.

    // this code is correct
    String result = null;
    if(obj instanceof String) {
      result = (String) obj;
    }

    // problem is here
    if (obj instanceof BlogPost) { // my code is lines 19 - 21. Confused on why It doesn't work
      // 1. cast "obj" to some blogPost, store it in variable, but not "result"
      // 2. assign to "result" variable result of getTitle() method applied to blogPost above
    }

    // correct
    return result;

Welcome to the Treehouse Community

Looking to learn something new?

Marcus Schumacher

Marcus Schumacher

SOS on Java Type Casting

1 Answer

Alexander Nikiforov

Alexander Nikiforov