强制从java.time中的`DateTimeFormatter.ofLocalized ...`生成的本地化字符串中的4位数年份 [英] Force 4-digit-year in localized strings generated from `DateTimeFormatter.ofLocalized…` in java.time

问题描述

java.time中的DateTimeFormatter 类提供了三个 ofLocalized ... 方法，用于生成表示包含一年的值的字符串。例如， ofLocalizedDate 。

The DateTimeFormatter class in java.time offers three ofLocalized… methods for generating strings to represent values that include a year. For example, ofLocalizedDate.

Locale l = Locale.US ; 
DateTimeFormatter f = DateTimeFormatter.ofLocalizedDate( FormatStyle.SHORT ).withLocale( l );
LocalDate today = LocalDate.now( ZoneId.of( "America/Chicago" ) );
String output = today.format( f );

对于我看过的语言环境，年份只有两位数字 FormatStyle 样式。

For the locales I have seen, the year is only two digits in the shorter FormatStyle styles.

如何让java.time本地化强制年份为四位数而不是两年？

How to let java.time localize yet force the years to be four digits rather than two?

我怀疑答案在于 DateTimeFormatterBuilder 类。但我找不到任何改变一年的长度的功能。我也仔细阅读了 Java 9源代码，但不能很好地解释该代码以找到答案。

I suspect the Answer lies in DateTimeFormatterBuilder class. But I cannot find any feature alter the length of year. I also perused the Java 9 source code, but cannot spelunk that code well enough to find an answer.

此问题类似于：

• 在java的simpledateformat中强制使用4位数年份


• Jodatime：如何打印4位数年份？

• forcing 4 digits year in java's simpledateformat
• Jodatime: how to print 4-digit year?

...但这些问题针对的是现在由java.time类取代的旧日期时间框架。

…but those Questions are aimed at older date-time frameworks now supplanted by the java.time classes.

推荐答案

没有内置的方法可以满足您的需求。但是，您可以应用以下解决方法：

There is no built-in method for what you want. However, you could apply following workaround:

Locale locale = Locale.ENGLISH;
String shortPattern =
    DateTimeFormatterBuilder.getLocalizedDateTimePattern(
        FormatStyle.SHORT,
        null,
        IsoChronology.INSTANCE,
        locale
    );
System.out.println(shortPattern); // M/d/yy
if (shortPattern.contains("yy") && !shortPattern.contains("yyy")) {
    shortPattern = shortPattern.replace("yy", "yyyy");
}
System.out.println(shortPattern); // M/d/yyyy

DateTimeFormatter shortStyleFormatter = DateTimeFormatter.ofPattern(shortPattern, locale);
LocalDate today = LocalDate.now(ZoneId.of("America/Chicago"));
String output = today.format(shortStyleFormatter);
System.out.println(output); // 11/29/2016

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