public void Reserve(int isbn, int user_id) throws IOException {
           int flag=0;
        for(int i=1;i<=5;i++)
            flag=B[i].Reserve(isbn,user_id);
        if(flag==1)
            System.out.println("\nThank You! Enjoy the book\n");
        else
            System.out.println("\nSorry we dont have that book\n");
    }