Валидатор требует корректно написанный конструктор для обоих классов. Все работает, но видимо что-то упустил.
package com.javarush.task.task15.task1504;
import java.util.LinkedList;
import java.util.List;
/*
ООП - книги
*/
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);
}
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(this.getBook() instanceof MarkTwainBook) return markTwainOutput;
if(this.getBook() instanceof AgathaChristieBook) return agathaChristieOutput;
return output;
}
public String toString() {
return getOutputByBookType();
}
}
public static class MarkTwainBook extends Book {
private String title;
MarkTwainBook(String title) {
super("Mark Twain");
this.title=title;
}
public MarkTwainBook getBook() {
return this;
}
public String getTitle() {
return this.title;
}
}
public static class AgathaChristieBook extends Book {
private String title;
AgathaChristieBook(String title) {
super("Agatha Christie");
this.title=title;
}
public AgathaChristieBook getBook() {
return this;
}
public String getTitle() {
return this.title;
}
}
}