更新单个列表项RXJava

Question

I basically want to convert this for loop to an Observable

private static List<Book> books

public static void replaceBook(Book book) {
    for (int i = 0; i < books.size(); i++) {
        if (books.get(i).getId().equals(book.getId())) {
            books.set(i, book);
        }
    }
}  

This is what I have so far but its not working. I thought the map operator would update the filtered item but I seem to be missing something.

Observable.from(books).filter(new Func1<Book, Boolean>() {
        @Override
        public Boolean call(Book b) {
            return b.getId().equals(book.getId());
        }
    }).map(new Func1<Book, Book>() {
        @Override
        public Book call(Book b) {
            return book;
        }
    }).subscribe();

Update

Based on Boris and Tassos's answers I got the following answer which seems to work

  Observable.from(books)
            .map(b -> b.getId().equals(book.getId()) ? book : b)
            .toList()
            .subscribe(s -> books = s);

Answer 1

Observable
  .from(books)
  .map(new Func1<Book, Book>() {
        @Override
        public Book call(Book b) {
            if (book.getId().equals(b.getId()))
                return book;
            return b;
        }
  })
  .toList()
  .subscribe();

Answer 2

Observable
  .from(books)
  .map(b ->  b.getId().equals(book.getId()) ? book : b)
  .subscribe();