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Java Java Data Structures Getting There Type Casting

Type Cast Challenge: If you cast obj as a BlogPost, how is it possible to return it when getTitle returns a String?

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

Not sure what I need to be doing here. If the obj is a BlogPost how can it be returned in a method that returns a String? Thanks!

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

1 Answer

cam, it's not possible and you don't return a BlogPost.

Try this code:

  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 p = (BlogPost) obj;
      result = p.getTitle();
    }
    return result;
  }

If it is a BlogPost you need to first get its title, and then return that, which is a String.