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Java Java Data Structures - Retired Getting There Type Casting

josh hahn
josh hahn
5,926 Points

unsure what is being asked here

i am unsure what is being asked here

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 = "";
    return result;
  }
}

1 Answer

Simon Coates
Simon Coates
28,694 Points

see comment

  public static String getTitleFromObject(Object obj) {
    // Fix this result variable to be the correct string.
  String result = "";   
 /* if(obj is a string) //use instanceof
    {
        //Assign obj as a string to result or return it directly from inside the condition. 
        //(you can cast and return in a single operation or two lines).
    }
    */    
    return result;
  }

This is a similar example that includes a test and a cast:

  static void method(Animal a) {  
    if(a instanceof Dog3){  
       Dog3 d=(Dog3)a;//downcasting  
       System.out.println("ok downcasting performed");  
    }  
  }

The key idea is that it test that the variable is of a subtype, then it has to tell java that the variable is able to be used as an instance of the subtype (requiring the cast).

For your tutorial, the obj is an obj, you have to tell java based on tests how to use the obj to get a string when obj is a string or a blogpost. If you want some code, visit https://teamtreehouse.com/community/need-some-help-to-execute-task-2 .