如何从模式创建Java时间瞬间? [英] How to create Java time instant from pattern?

问题描述

考虑一个代码:

TemporalAccessor date = DateTimeFormatter.ofPattern("yyyy-MM-dd").parse("9999-12-31");
Instant.from(date);

最后一行抛出异常:

Unable to obtain Instant from TemporalAccessor: {},ISO resolved to 9999-12-31 of type java.time.format.Parsed

如何从yyyy-MM-dd模式创建Instant?

推荐答案

字符串"9999-12-31"仅包含有关日期的信息.它不包含有关时间或偏移量的任何信息.因此，没有足够的信息来创建Instant. (其他日期和时间库更为宽松，但java.time避免默认使用这些值)

The string "9999-12-31" only contains information about a date. It does not contain any information about the time-of-day or offset. As such, there is insufficient information to create an Instant. (Other date and time libraries are more lenient, but java.time avoids defaulting these values)

您的首选是使用LocalDate而不是`Instant:

Your first choice is to use a LocalDate instead of an `Instant:

LocalDate date = LocalDate.parse("9999-12-31");

您的第二个选择是对日期进行后期处理，以将其转换为需要时区(此处选择为巴黎)的瞬间:

Your second choice is to post process the date to convert it to an instant, which requires a time-zone, here chosen to be Paris:

LocalDate date = LocalDate.parse("9999-12-31");
Instant instant = date.atStartOfDay(ZoneId.of("Europe/Paris")).toInstant();

您的第三个选择是将时区添加到格式化程序中，并默​​认为日期时间:

Your third choice is to add the time-zone to the formatter, and default the time-of-day:

static final DateTimeFormatter FMT = new DateTimeFormatterBuilder()
    .appendPattern("yyyy-MM-dd")
    .parseDefaulting(ChronoField.NANO_OF_DAY, 0)
    .toFormatter()
    .withZone(ZoneId.of("Europe/Paris"));
Instant instant = FMT.parse("9999-31-12", Instant::from);

(如果这不起作用，请确保您具有最新的JDK 8版本，因为该区域中的错误已得到修复.)

(If this doesn't work, ensure you have the latest JDK 8 release as a bug was fixed in this area).

值得注意的是，这些可能性都不直接使用TemporalAccessor，因为该类型是低级框架接口，不是大多数应用程序开发人员都可以使用的接口.

It is worth noting that none of these possibilities use TemporalAccessor directly, because that type is a low-level framework interface, not one for most application developers to use.

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