区域设置的Java日期格式

Question

如何找到给定Locale的DateFormat ？

Answer 1

DateFormat.getDateInstance(int,Locale)

For example:

import static java.text.DateFormat.*;

DateFormat f = getDateInstance(SHORT, Locale.ENGLISH);

Then you can use this object to format Date s:

String d = f.format(new Date());

If you actually want to know the underlying pattern (eg yyyy-MMM-dd ) then, as you'll get a SimpleDateFormat object back:

SimpleDateFormat sf = (SimpleDateFormat) f;
String p1 = sf.toPattern();
String p2 = sf.toLocalizedPattern();

Answer 2

tl;dr

DateTimeFormatter.ofLocalizedDateTime( FormatStyle.FULL )
                 .withLocale( Locale.CANADA_FRENCH );

java.time

The original date-time classes are now legacy and have been supplanted by the java.time classes.

The DateTimeFormatter has a simple way to localize automatically by Locale when generating a String to represent the date-time value. Specify a FormatStyle to indicate length of output (abbreviated or not).

DateTimeFormatter f = DateTimeFormatter.ofLocalizedDateTime( FormatStyle.FULL );
f = f.withLocale( Locale.CANADA_FRENCH );

Get the current moment. Notice that Locale and time zone have nothing to do with each other. One determines presentation, the other adjusts into a particular wall-clock time . So you can have a time zone in New Zealand with a Locale of Japanese, or in this case a time zone in India with presentation formatted for a Québécois person to read.

ZoneId z = ZoneId.of( "Asia/Kolkata" );
ZonedDateTime zdt = ZonedDateTime.now( z );

Generate a String using that localizing formatter object.

String output = zdt.format( f );

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About java.time

The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date , Calendar , & SimpleDateFormat .

The Joda-Time project, now in maintenance mode , advises migration to the java.time classes.

To learn more, see the Oracle Tutorial . And search Stack Overflow for many examples and explanations. Specification is JSR 310 .

Where to obtain the java.time classes?

• Java SE 8 , Java SE 9 , and later
  • Built-in.
  • Part of the standard Java API with a bundled implementation.
  • Java 9 adds some minor features and fixes.
• Java SE 6 and Java SE 7
  • Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport .
• Android
  • The ThreeTenABP project adapts ThreeTen-Backport (mentioned above) for Android specifically.
  • See How to use ThreeTenABP… .

The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval , YearWeek , YearQuarter , and more .