BlogPost typecasting

Question

I'm stuck at the 2nd challenge of the last exercise on "Getting There" of the Java Data Structures course.

I keep getting the wrong result. Any suggestions?

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) {
    boolean objIsString = obj instanceof String;
    boolean objIsBlogPost = obj instanceof BlogPost;
    String result = "";

    if (objIsString == true) {
      result = (String)obj;
    }

    if (objIsBlogPost == true) {
      result = ((BlogPost)obj).toString(); 
    }

   return result;
  }
}

Answer 1 · 2017-06-06T15:35:00Z

June 6, 2017 3:35pm

Your code is practically correct. The only issue is that the instructions specified that when a BlogPost object is passed in it wants the title of the BlogPost to be returned, not the toString version of the BlogPost.

You can get the title of the BlogPost by calling its getTitle method, 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;
  public static boolean HINT_2_ENABLED = false;

  public static String getTitleFromObject(Object obj) {
    boolean objIsString = obj instanceof String;
    boolean objIsBlogPost = obj instanceof BlogPost;
    String result = "";

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

    if (objIsBlogPost) {
      result = ((BlogPost)obj).getTitle();  // toString replaced with getTitle
    }

   return result;
  }
}

You might also notice that I removed the == true part of your conditions due to them being unnecessary. The result of the instanceof keyword is by itself a boolean so you don't have to compare it to anything to make the if statements work.

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Bjorn Van de Weyngaert

Bjorn Van de Weyngaert

BlogPost typecasting

1 Answer

andren

andren