I am unable to understand the second task. In the first task I checked if the passed object is string and returned it.

Question

Please help me understand how to cast obj to BlogPost and is it down cast or up cast. also how to return the results of the getTitle method on the newly type casted BlogPost instance.

Thank you

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;}

    BlogPost blogpost = (BlogPost) obj;

    return result;
  }
}

Answer 1 · 2015-05-29T14:07:12Z

May 29, 2015 2:07pm

The cast is a down cast because we are going from the base type Object to BlogPost. The syntax of the cast is correct, but this needs to be enclosed in an else if statement. The obj will be either a String or a BlogPost. The first case (i.e. String) is taken care of by the if statement, now we need to code for the second cases where obj is a BlogPost.

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 BlogPost) {
      BlogPost temp = (BlogPost) obj;
      result = temp.getTitle();
    }
    return result;
  }

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CHIRAG SARAOGI

CHIRAG SARAOGI

I am unable to understand the second task. In the first task I checked if the passed object is string and returned it.

1 Answer

Allan Clark

Allan Clark

CHIRAG SARAOGI

CHIRAG SARAOGI