如何在JSR 310中处理大写或小写？ [英] How to handle upper or lower case in JSR 310?

问题描述

如果一个月是UPPER或小写，即不是Title情况，则DateTimeFormatter无法解析日期。是否有一种简单的方法将日期转换为标题案例，或者使格式化程序更宽松的方法？

If a month is in UPPER or lower case, i.e. not Title case, DateTimeFormatter cannot parse the date. Is there a simple way to convert a date to title case, or a way to make the formatter more lenient?

for (String date : "15-JAN-12, 15-Jan-12, 15-jan-12, 15-01-12".split(", ")) {
    try {
        System.out.println(date + " => " + LocalDate.parse(date,
                                     DateTimeFormatter.ofPattern("yy-MMM-dd")));
    } catch (Exception e) {
        System.out.println(date + " => " + e);
    }
}

打印

15-JAN-12 => java.time.format.DateTimeParseException: Text '15-JAN-12' could not be parsed at index 3
15-Jan-12 => 2015-01-12
15-01-12 => java.time.format.DateTimeParseException: Text '15-01-12' could not be parsed at index 3
15-jan-12 => java.time.format.DateTimeParseException: Text '15-jan-12' could not be parsed at index 3

推荐答案

DateTimeFormatter 默认情况下是严格且区分大小写的。使用 DateTimeFormatterBuilder 并指定 parseCaseInsensitive（）来解析不区分大小写。

DateTimeFormatters are strict and case sensitive by default. Use a DateTimeFormatterBuilder and specify parseCaseInsensitive() to parse case insensitive.

DateTimeFormatter formatter = new DateTimeFormatterBuilder()
    .parseCaseInsensitive()
    .appendPattern("yy-MMM-dd")
    .toFormatter(Locale.US);

能够解析数字月份（即15-01- 12），你还需要指定 parseLenient（）。

To be able to parse numeric months (ie. "15-01-12"), you also need to specify parseLenient().

DateTimeFormatter formatter = new DateTimeFormatterBuilder()
    .parseCaseInsensitive()
    .parseLenient()
    .appendPattern("yy-MMM-dd")
    .toFormatter(Locale.US);

您还可以更详细地将月份部分指定为不区分大小写/宽松：

You can also be more verbose to specify only the month part as case insensitive/lenient:

DateTimeFormatter formatter = new DateTimeFormatterBuilder()
    .appendPattern("yy-")
    .parseCaseInsensitive()
    .parseLenient()
    .appendPattern("MMM")
    .parseStrict()
    .parseCaseSensitive()
    .appendPattern("-dd")
    .toFormatter(Locale.US);

从理论上讲，这可能会更快，但我不确定是不是。

In theory, this could be faster, but I'm not sure if it is.

PS：如果在年份部分之前指定 parseLenient（），它还将解析4位数年份（即2015-JAN-12）正确。

PS: If you specify parseLenient() before the year part, it will also parse 4 digit years (ie. "2015-JAN-12") correctly.

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