如何在Java流处理中存储中间状态

Question

我有以下Java循环：

for (final Long orderNumber : availableOrderIds) {
    final List<ReservationDetailResponse> reservations = tryToReserve(orderNumber);
    if (successful(reservations)) {
        return withReservationIdFrom(reservations);
    }
}

和方法：

private boolean successful(final List<ReservationDetailResponse> reservations) {
    return !reservations.isEmpty();
}

private Long withReservationIdFrom(final List<ReservationDetailResponse> reservations) {
    return reservations.get(0).getReservationId();
} 

如何将其转换为流处理？

感谢您的帮助！

Answer 1

使用map进行转换，使用filter进行条件和findFirst，您可以做类似的事情：

return availableOrderIds.stream()
        .map(this::tryToReserve)
        .filter(this::successful)
        .findFirst()
        .map(this::withReservationIdFrom)
        .orElse(0L); // assumed as default value

Answer 2

遵循以下内容：

availableOrderIds.stream()
   .map(orderNumber -> tryToReserve(orderNumber))
   .filter(reservation -> successful(reservations))
   .map(reservations -> withReservationIdFrom(reservations))
   .findFirst()
   .get();