Output is correct, failing 4 requirements still

Question about the task

Under discussion

I struggled to get to this point, and it felt so good to have done it without needing help, but now, when it looks like everything is being done correctly, I can't figure it out.

1. Create a public static class MarkTwainBook that inherits Book. Name of the author [Mark Twain].
The constructor parameter is the book title.
2. Implement all the abstract methods in the MarkTwainBook class.
3. Change the return type of the getBook method to make it more appropriate.
4. In a similar manner, create the AgathaChristieBook class. Name of the author [Agatha Christie].
5. In the Book class, implement the getOutputByBookType method so that it returns:
5.1. agathaChristieOutput for books written by Agatha Christie;
5.2. markTwainOutput for books written by Mark Twain.

Requirements:

The Solution class must contain the public static MarkTwainBook class.
The MarkTwainBook class must be a descendant of the Book class.
The MarkTwainBook class must correctly implement a constructor with one String parameter (book title).
The MarkTwainBook class constructor should call the constructor of the parent class (Book) with the argument "Mark Twain".
The getBook method in the MarkTwainBook class must have the MarkTwainBook return type and return the current object.
The Solution class must contain the public static AgathaChristieBook class.
The AgathaChristieBook class must be a descendant of the Book class.
The AgathaChristieBook class must correctly implement a constructor with one String parameter (book title).
The AgathaChristieBook class constructor should call the constructor of the parent class (Book) with the argument "Agatha Christie".
The getBook method in the AgathaChristieBook class must have the AgathaChristieBook return type and return the current object.
The getTitle method in the AgathaChristieBook and MarkTwainBook classes should return the title of a specific book.
The getOutputByBookType method must return the correct string for AgathaChristieBook objects.
The getOutputByBookType method must return the correct string for MarkTwainBook objects.
The MarkTwainBook class must have a String field title (book title).
The AgathaChristieBook class must have a String field title (book title).

package com.codegym.task.task15.task1504; import java.util.LinkedList; import java.util.List; /* OOP: Books */ public class Solution { public static void main(String[] args) { List<Book> books = new LinkedList<Book>(); books.add(new MarkTwainBook("Tom Sawyer")); books.add(new AgathaChristieBook("Hercule Poirot")); System.out.println(books); } public static class MarkTwainBook extends Book { private String author = "Mark Twain"; String title; MarkTwainBook (String title) { super("Mark Twain"); this.title = title; } public String getTitle() { return title; } public MarkTwainBook getBook() { return new MarkTwainBook(title); } } public static class AgathaChristieBook extends Book { private String author = "Agatha Christie"; String title; AgathaChristieBook (String title) { super("Agatha Christie"); this.title = title; } public String getTitle() { return title; } public AgathaChristieBook getBook() { return new AgathaChristieBook(title); } } abstract static class Book { private String author; public Book(String author) { this.author = author; } public abstract Book getBook(); public abstract String getTitle(); private String getOutputByBookType() { String agathaChristieOutput = author + ": " + getBook().getTitle() + " is a detective"; String markTwainOutput = getBook().getTitle() + " was written by " + author; String output = "output"; if (getBook() instanceof AgathaChristieBook) output = agathaChristieOutput; if (getBook() instanceof MarkTwainBook) output = markTwainOutput; return output; } public String toString() { return getOutputByBookType(); } } }

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Oliver Heintz

Level 18 , Mustang, United States

9 January 2021, 06:09

Somehow, by deleting the line:

private String author = "Mark Twain";

and the corresponding one for Agatha Christie, it fixed the error with the getBook method. And I don't understand that, either.

Guadalupe Gagnon

Level 37 , Tampa, United States

9 January 2021, 19:16

The variable author is already implemented from the Book class, which both of those descend from. By making an author field in those classes you would be hiding the correct author field inherited from Book. The other problem in this code is that the task says that the getBook() method should return the current object, however they both are returning new objects. There is a keyword that allows returning the current object. Find this keyword and fix your getBook() methods to return the proper object and you should pass.

Oliver Heintz

Level 18 , Mustang, United States

9 January 2021, 19:55

I actually changed both of those within minutes of posting this last night, but to no avail. This is what I have now:

public static class MarkTwainBook extends Book {
        String title;

        MarkTwainBook (String title) {
            super("Mark Twain");
            this.title = title;
        }

        public String getTitle() {
            return title;
        }

        public MarkTwainBook getBook() {
            return MarkTwainBook.this;
        }
    }

Apparently I'm still not implementing the Constructor correctly.

Guadalupe Gagnon

Level 37 , Tampa, United States

9 January 2021, 20:00

use just return this, not MarkTwainBook.this

Oliver Heintz

Level 18 , Mustang, United States

10 January 2021, 15:11

I needed to make my constructors public. Thanks for taking the time to help, though.