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Java Java Data Structures - Retired Getting There Type Casting

Kenneth Balajadia
Kenneth Balajadia
2,009 Points

The method getTitleFromObject will be called and passed a String and/or a com.example.BlogPost. For this first task, ret

The method getTitleFromObject will be called and passed a String and/or a com.example.BlogPost. For this first task, return the object obj type casted as a String if it is in fact a String.

I've included BlogPost.java for your reference only.

i dont know how to figure it out the hint 2. after i click recheck work it says

Bummer! Hint 2: you can cast an object to a string like this (String) obj

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 = true;

  public static String getTitleFromObject(Object obj) {
    // Fix this result variable to be the correct string.
    if (obj instanceof String) {
      return (String) obj;
    } else {
      return ((BlogPost) obj).getTitle(); 
    }
  }
}

4 Answers

Grigorij Schleifer
Grigorij Schleifer
10,365 Points

Hy Kenneth,

I have fixed it :smiley:

public static String getTitleFromObject(Object obj) {

    String result = ""; // use the String to store the Title from BlogPost
     if (obj instanceof String) {
      return (String) obj;
    } else {
      result = ((BlogPost) obj).getTitle(); // store the Title from BlogPost into result
    }
    return result; // return Title if obj is a BlogPost
  }

Makes sense?

Grigorij

Alberto Castro
Alberto Castro
9,311 Points

I have just one question what is the reason for the parenthesis I'm pointing at here

--->((BlogPost) obj)<---.getTitle()

Why is not

(BlogPost) obj.getTitle()
Kentessa Fanfair
Kentessa Fanfair
11,261 Points

The reason for the parenthesis is to ensure that the object will be typecast as BlogPost before the getTitle() method is called. Since the getTitle() method belongs to the BlogPost class if you chain that method to an object before it is typecast the compiler might throw an error because the object is not of type BlogPost therefore getTitle() method does not exist on said object.

charles holder
charles holder
1,944 Points

so slightly confused on... get title takes a String and returns and String so how is it used on the obj that is being cast to BlogPost if BlogPost Is not a String? thanks in advane.

hello.! guys. I'm rookie. how did you know the answer of that question? I couldn't figure out even the first part of the answer. the only part that I can figure out was the "if()" and was because I did a search.

can you explain me how to figure out an answer for those type of question? thx.

Norbert Weinkauf
PLUS
Norbert Weinkauf
Courses Plus Student 2,293 Points

The first task didn't work for me either. I've had had to give the right answer of the second task for the first. It seems to a bug. I guess the right answer to the first quesstion would just be:

return (String) obj;