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Java Java Data Structures Getting There Type Casting

Raslan Ismail
Raslan Ismail
10,262 Points
Posted by Raslan Ismail
Raslan Ismail
10,262 Points

can somebody help me?!

i didn't understand the question

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;
  }

    return result;
  }
}

1 Answer

Steve Hunter
Steve Hunter
57,712 Points

Hi there,

Your code passes task one just fine - good work!

The second task needs you to set the result variable to a string. If you are in the else clause, we know that obj is of type BlogPost; that's defined in the first task.

So, cast obj to a BlogPost. Then call the getTitle() method on that casted obj (just surround that in parentheses). Either return that directly, or assign the result to result then return that.

This looks like the following; let's start with the cast:

result = (BlogPost) obj;

But, the method returns a String - we need to get the title of the post; we can use the getTitle() method by surrounding the above in parentheses and using dot notation:

result = ((BlogPost) obj).getTitle();

That can be placed either in the else clause of the if statement, or within a new if statement.:

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

// or

  public static String getTitleFromObject(Object obj) {
    if(obj instanceof String){
      return (String) obj;
    } else {
      return ((BlogPost) obj).getTitle();
    }
  }

// or

  public static String getTitleFromObject(Object obj) {
    String result = "";
    if(obj instanceof String){
      result = (String) obj;
    } 
    if(obj instanceof BlogPost){
      result = ((BlogPost) obj).getTitle();
    }
    return result;
  }

There are other alternatives; I hope that helped.

Steve.