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Java Java Data Structures - Retired Getting There Type Casting

Abe Daniels
PLUS
Abe Daniels
Courses Plus Student 2,781 Points
Posted by Abe Daniels
Abe Daniels
Courses Plus Student 2,781 Points

Need help typecasting

This code works fine for the obj/String typecast. Tried switching up a few params to see if i could BlogPost to work, but to no avail. Any pointers? Thanks :)

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

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

1 Answer

Allan Clark
Allan Clark
10,810 Points
Allan Clark
Allan Clark
10,810 Points 
    if(obj instanceof BlogPost) {
      String result = (String) BlogPost;
      return result;
    }

This tells Java to cast the object BlogPost into a String and then return it. We don't have a BlogPost object (it is a class), we are casting the obj variable into a BlogPost then returning the title. Change your cast statement to:

BlogPost result = (BlogPost) obj;

Then return the title using the accessor method.

Jeeya M
Jeeya M
16,839 Points

Allan Clark how do you do the return method

Allan Clark
Allan Clark
10,810 Points
Allan Clark
Allan Clark
10,810 Points

instead of returning the whole result variable, we only need the title of the BlogPost saved under result. so we can return it like this: 

return result.getTitle();