Java 8 DateTimeFormatter解析可选部分 [英] Java 8 DateTimeFormatter parsing optional sections

问题描述

我需要将日期时间解析为两种不同格式的字符串:

I need to parse date-times as strings coming as two different formats:

• 19861221235959Z
• 1986-12-21T23:59:59Z

以下dateTimeFormatter模式可以正确解析第一种日期字符串

The following dateTimeFormatter pattern properly parses the first kind of date strings

DateTimeFormatter.ofPattern ("uuuuMMddHHmmss[,S][.S]X")

但第二个失败，因为破折号，冒号和T不在预期范围内.

but fails on the second one as dashes, colons and T are not expected.

我试图使用可选部分，如下所示:

My attempt was to use optional sections as follows:

DateTimeFormatter.ofPattern ("uuuu[-]MM[-]dd['T']HH[:]mm[:]ss[,S][.S]X")

出乎意料的是，这会解析第二种日期字符串(带破折号的日期字符串)，而不是第一种日期字符串，并抛出一个

Unexpectedly, this parses the second kind of date strings (the one with dashes), but not the first kind, throwing a

java.time.format.DateTimeParseException: Text '19861221235959Z' could not be parsed at index 0

好像可选部分没有被评估为可选...

It's as if optional sections are not being evaluated as optional...

推荐答案

正如Peter在评论中所述，问题在于您的模式将整个字符串视为年份.您可以使用.appendValue(ChronoField.YEAR, 4)将其限制为四个字符:

As Peter stated in the comments, the problem is that your pattern is considering the entire string as the year. You can use .appendValue(ChronoField.YEAR, 4) to limit it to four characters:

DateTimeFormatter formatter = new DateTimeFormatterBuilder()
    .appendValue(ChronoField.YEAR, 4)
    .appendPattern("[-]MM[-]dd['T']HH[:]mm[:]ss[,S][.S]X")
    .toFormatter();

这可以正确解析您的两个示例.

This parses correctly with both of your examples.

如果您想变得更加冗长，可以这样做:

If you fancy being even more verbose, you could do:

DateTimeFormatter formatter = new DateTimeFormatterBuilder()
    .appendValue(ChronoField.YEAR, 4)
    .optionalStart().appendLiteral('-').optionalEnd()
    .appendPattern("MM")
    .optionalStart().appendLiteral('-').optionalEnd()
    .appendPattern("dd")
    .optionalStart().appendLiteral('T').optionalEnd()
    .appendPattern("HH")
    .optionalStart().appendLiteral(':').optionalEnd()
    .appendPattern("mm")
    .optionalStart().appendLiteral(':').optionalEnd()
    .appendPattern("ss")
    .optionalStart().appendPattern("X").optionalEnd()
    .toFormatter();

这篇关于Java 8 DateTimeFormatter解析可选部分的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！