---JAVA---

Question

i don't understand how to do this; i would appreciate help :)

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

Answer 1 · 2018-02-05T10:12:25Z

February 5, 2018 10:12am

You just need to do what you've already done for the String but with the BlogPost object instead,

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

Answer 2 · 2018-02-05T11:33:51Z

February 5, 2018 11:33am

Correct but if you look at the specification, the obj object can only exist in two states; a String or a BlogPost. That said, there's no need to directly test the second condition; if the first condition fails, then obj isn't a String so it must be a BlogPost.

You can just do the cast in the else clause. You can use the result variable to hold each respective result and return it after the if conditional has run, or you can return either option directly within each condition. Having two return statements is sometimes frowned upon, but where they are mutually exclusive, i.e. both can never run, it's less of an offence.

    if(obj instanceof String){
      return (String) obj;
    } else {
      return ((BlogPost) obj).getTitle();
    }

Alternatively, do as above and set result to the cast object and return result at the end of the method.

Steve.

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Damjan Vlaic

Damjan Vlaic

---JAVA---

i don't understand how to do this; i would appreciate help :)

2 Answers

calp

calp

Damjan Vlaic

Damjan Vlaic

Steve Hunter

Steve Hunter

Damjan Vlaic

Damjan Vlaic

calp

calp

Steve Hunter

Steve Hunter