New to Java

I'm making a Library class that's supposed to be able to store book objects from a book class, and I seem to be running into a problem at the for-each loop.

Main class:

package library;
import java.util.Scanner;

public class Main {

public static void main(String[] args) {
    {
        Scanner k = new Scanner(System.in);
        String[] subject = { "Russian", "Literature" };
        Book X = new Book("Misanthrope", "Penguin Co.", "Uncle Vanya, Rakolnikov", subject, 10213, 1835, true);
        Library Shelf = new Library();
        Shelf.add(X);
        System.out.println("Enter Subject you'd like to search"); //Prompt for Subject Search method

        String G = k.next();
        Shelf.SearchBySubject(G);
        }
    }
}

Library Class:

p

ackage library;
import java.util.ArrayList;

public class Library {
    private ArrayList list = new ArrayList();       //Declare Private ArrayLists
    private ArrayList ResultList = new ArrayList();
    private String B[];

        public void add(Book Y)  //add method for adding books into
        {                        //Array list
            list.add(Y);
        }

        public void SearchBySubject(String G)  //Method so Search By Subject
        {                                      //Using Array lists and Foreach
            for(Book z: list){
                B = z.GetSubject();
                if(B.contains(G))
                {
                    ResultList.add(z);
                }
            }
            for(Book X: ResultList)
            {
                System.out.println("Title: " + X.GetTitle() + " Authors: " + X.GetAuthor() +
                    " ID Number: " + X.GetNum());
            }
        }
}

Book Class:

package library;

public class Book extends Library {
private String Title, Publisher, Authors;
        private String[] Subject;
        private int CatalogNumber, Year;
        private boolean Circulating;
                                // Book Constructor
        public Book(String title, String publisher, String authors, String[] subject, int catnum, int year, boolean circ)
        {
            Title = title;
            Publisher = publisher;
            Authors = authors;
            Subject = subject;
            CatalogNumber = catnum;
            Year = year;
            Circulating = circ;
        }
                                            //Series for Get Methods
        public String[] GetSubject() //Get Subject String
        {
            return Subject;
        }

        public String GetTitle()  //Get Title String
        {
            return Title;
        }

        public int GetNum()  //Get CatalogNumber Integer
        {
            return CatalogNumber;
        }

        public String GetAuthor() // Get Authors String
        {
            return Authors;
        }
    }

The specific error I'm receiving is:
"incompatible types
required: library.Book
found: java.lang.Object"

The 2 specific lines with problems are:

for(Book z: list){

for(Book X: ResultList)

Any help you could provide would be very appreciated. Been stuck on it for awhile, and tried browsing forums to find the information but had no luck.

Thanks!