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Java Java Data Structures Getting There Type Casting

Posted by David Jones
David Jones
1,681 Points

How to only return one vale while using type casting inside a method.

I am having trouble with type casting. I understand using instanceof and I answered the first half of the problem correctly. Now that I need to add another instanceof I can't figure out how to return something that either be a String or BlogPost.

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


  }
}

1 Answer

Jeremy Hill
Jeremy Hill
29,567 Points
Jeremy Hill
Jeremy Hill
29,567 Points

Here is what I did:

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

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