java - 链接多个 Java 可选值

Question

private void validatePGTimingRestrictions(
        Listing listing,
        ListingAutoVerificationResponse listingAutoVerificationResponse) {
    if (Optional.ofNullable(listing.getLastEntryTime()).isPresent()
            && Optional.ofNullable(listing.getTimingRestrictions()).isPresent()
            && !listing.getTimingRestrictions()) {
        listingAutoVerificationResponse.getRejectReasons()
                .add(ListingAutoVerificationErrorMessages.PG_LISTING_TIMING_ERROR);
    }
}

如何使用链接选项和 orElseGet 优化此代码。listing.getTimingRestrictions() 返回 boolean 值，listing.getLastEntryTime() 返回字符串，List 中的 add 方法也返回 boolean 值。

Answer 1

您可以映射可选到完全不同的值，从而允许您链接空检查:

Object a, b, c;
....
Optional.ofNullable(a) // null-check for 'a'
    .map(x -> b) // null-check for 'b'
    .map(x -> c) // null-check for 'c'
    .ifPresent(x -> ...) // do something with a,b,c

就您而言:

Optional.ofNullable(listing.getLastEntryTime())
    .map(x -> listing.getTimingRestrictions())
    .filter(x -> !x)
    .ifPresent(x -> ... ); // do something with the listing