public static Long save(Book book) {
long id = book.getId() == null ? ++LAST_ADDED_ID : book.getId();
book.setId(id);
book.increaseVersion();
int indexOf = STORE.indexOf(book);
if (indexOf == -1) {
STORE.add(book);
} else {
STORE.set(indexOf, book);
}
return id;
}
