在 java.time 中从 `DateTimeFormatter.ofLocalized...` 生成的

问题描述

DateTimeFormatter java.time 中的类提供了三个 ofLocalized… 方法来生成字符串来表示包含年份的值.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 );

对于我所看到的语言环境，年份只有两位数，较短的 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位?

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年份长度的功能.我还仔细阅读了 Java 9 源代码，但无法很好地挖掘该代码以找到答案.

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.

这个问题类似于:

• 在 java 的 simpledateformat 中强制使用 4 位数年份
• Jodatime:如何打印 4 位数年份?

...但是这些问题针对的是现在被 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

没有你想要的内置方法.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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