getOutPutByBookType()????

Question about the task

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In getOutPutByBookType() i think i need to work with instanceof Agatha... and Mark...but i dont know what to instanceof. This is so frustrating!!! 🤦‍♂️

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{ public String title; public MarkTwainBook(String bookTitle){ super("Mark Twain"); this.title=bookTitle; } @Override public MarkTwainBook getBook() { return MarkTwainBook.this; } @Override public String getTitle() { return title; } } public static class AgathaChristieBook extends Book{ public String title; public AgathaChristieBook(String bookTitle){ super("Agatha Christie"); this.title=bookTitle; } @Override public AgathaChristieBook getBook() { return AgathaChristieBook.this; } @Override public String getTitle() { return 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(???? instanceof AgathaChristieBook){ output = agathaChristieOutput }else if(????? instanceof MarkTwainBook){ output = markTwainOutput; } return output; } public String toString() { return getOutputByBookType(); } } }

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Thomas

Level 31 , Bayreuth, Germany

7 July 2020, 14:44

Try the current object... this

Angel Stefan Arjoca

Level 26 , Bucharest, Romania

7 July 2020, 15:03

So, i need to do: if(this instanceof Agatha...) //Agatha...instanceof Agatha...??? I don't think i understand this concept, is logic that an object is "equal" with the same object, what is the purpose of coding like this!? Can explain to me, pls!? Tk you!

Thomas

Level 31 , Bayreuth, Germany

7 July 2020, 15:24

you have a class Book and descendants of it, Agatha and Twain. Eg in the main you create a book mark of the class Twain. Now you can call all Twain methods on that mark book and of course all Book methods, too. And you can collect all Book types in a list. To call the Twain methods on the mark book you need to check if it's from type Twain. Or, like here, Book is abstract and you can call the Book methods on all descendants but separate the behavior depending on the descendants class. So it's not like if Agatha instanceof Agatha but if Book instanceof Agatha