链接多个Java选项

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优化这段代码。listing.getTimingRestrictions()返回布尔值，listing.getLastEntryTime()从列表返回String & add方法也返回布尔值。

Answer 1

您可以将 Optional 映射到一个完全不同的值，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

就你而言：

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

Answer 2

你为什么要在那里使用可选的？

if (listing.getLastEntryTime() != null && !listing.getTimingRestrictions()) {
listingAutoVerificationResponse.getRejectReasons()
           .add(ListingAutoVerificationErrorMessages.PG_LISTING_TIMING_ERROR);
}

因为getTimingRestrictions是布尔型的，而且是一个基本类型，所以它不应该是null。

Answer 3

如果我一切都做对了..。：

if(listing.getLastEntryTime() != null){
    Optional.ofNullable(listing.getTimingRestrictions())
            .filter(x -> !x)
            .ifPresent(x -> <do whatever you want with x here>)
}