非 ISO 日期转换
原文: https://docs.oracle.com/javase/tutorial/datetime/iso/nonIso.html
本教程不会详细讨论 java.time.chrono
包。但是,知道此软件包提供了几个非基于 ISO 的预定义年表可能会很有用,例如日语,Hijrah,Minguo 和 Thai Buddhist。您也可以使用此包创建自己的年表。
本节介绍如何在其中一个预定义的年表中转换基于 ISO 的日期和日期。
转换为非基于 ISO 的日期
您可以使用来自(TemporalAccessor)方法的将基于 ISO 的日期转换为另一个年代的日期,例如 [
JapaneseDate.from(TemporalAccessor)](https://docs.oracle.com/javase/8/docs/api/java/time/chrono/JapaneseDate.html#from-java.time.temporal.TemporalAccessor-) 。如果此方法无法将日期转换为有效实例,则抛出
DateTimeException。以下代码将
LocalDateTime实例转换为若干预定义的非 ISO 日历日期:
LocalDateTime date = LocalDateTime.of(2013, Month.JULY, 20, 19, 30);
JapaneseDate jdate = JapaneseDate.from(date);
HijrahDate hdate = HijrahDate.from(date);
MinguoDate mdate = MinguoDate.from(date);
ThaiBuddhistDate tdate = ThaiBuddhistDate.from(date);
`StringConverter
`例子从LocalDate
转换为ChronoLocalDate
到String
和背部。 toString
方法采用LocalDate
和Chronology
的实例,并使用提供的Chronology
返回转换后的字符串。 DateTimeFormatterBuilder
用于构建可用于打印日期的字符串:
/**
* Converts a LocalDate (ISO) value to a ChronoLocalDate date
* using the provided Chronology, and then formats the
* ChronoLocalDate to a String using a DateTimeFormatter with a
* SHORT pattern based on the Chronology and the current Locale.
*
* @param localDate - the ISO date to convert and format.
* @param chrono - an optional Chronology. If null, then IsoChronology is used.
*/
public static String toString(LocalDate localDate, Chronology chrono) {
if (localDate != null) {
Locale locale = Locale.getDefault(Locale.Category.FORMAT);
ChronoLocalDate cDate;
if (chrono == null) {
chrono = IsoChronology.INSTANCE;
}
try {
cDate = chrono.date(localDate);
} catch (DateTimeException ex) {
System.err.println(ex);
chrono = IsoChronology.INSTANCE;
cDate = localDate;
}
DateTimeFormatter dateFormatter =
DateTimeFormatter.ofLocalizedDate(FormatStyle.SHORT)
.withLocale(locale)
.withChronology(chrono)
.withDecimalStyle(DecimalStyle.of(locale));
String pattern = "M/d/yyyy GGGGG";
return dateFormatter.format(cDate);
} else {
return "";
}
}
对于预定义的年表,使用以下日期调用方法时:
LocalDate date = LocalDate.of(1996, Month.OCTOBER, 29);
System.out.printf("%s%n",
StringConverter.toString(date, JapaneseChronology.INSTANCE));
System.out.printf("%s%n",
StringConverter.toString(date, MinguoChronology.INSTANCE));
System.out.printf("%s%n",
StringConverter.toString(date, ThaiBuddhistChronology.INSTANCE));
System.out.printf("%s%n",
StringConverter.toString(date, HijrahChronology.INSTANCE));
输出如下所示:
10/29/0008 H
10/29/0085 1
10/29/2539 B.E.
6/16/1417 1
转换为基于 ISO 的日期
您可以使用静态 LocalDate.from
方法从非 ISO 日期转换为LocalDate
实例,如以下示例所示:
LocalDate date = LocalDate.from(JapaneseDate.now());
其他基于时间的类也提供此方法,如果无法转换日期,则抛出DateTimeException
。
来自 `StringConverter
`示例的fromString
方法解析包含非 ISO 日期的String
并返回一个LocalDate
实例。
/**
* Parses a String to a ChronoLocalDate using a DateTimeFormatter
* with a short pattern based on the current Locale and the
* provided Chronology, then converts this to a LocalDate (ISO)
* value.
*
* @param text - the input date text in the SHORT format expected
* for the Chronology and the current Locale.
*
* @param chrono - an optional Chronology. If null, then IsoChronology
* is used.
*/
public static LocalDate fromString(String text, Chronology chrono) {
if (text != null && !text.isEmpty()) {
Locale locale = Locale.getDefault(Locale.Category.FORMAT);
if (chrono == null) {
chrono = IsoChronology.INSTANCE;
}
String pattern = "M/d/yyyy GGGGG";
DateTimeFormatter df = new DateTimeFormatterBuilder().parseLenient()
.appendPattern(pattern)
.toFormatter()
.withChronology(chrono)
.withDecimalStyle(DecimalStyle.of(locale));
TemporalAccessor temporal = df.parse(text);
ChronoLocalDate cDate = chrono.date(temporal);
return LocalDate.from(cDate);
}
return null;
}
使用以下字符串调用方法时:
System.out.printf("%s%n", StringConverter.fromString("10/29/0008 H",
JapaneseChronology.INSTANCE));
System.out.printf("%s%n", StringConverter.fromString("10/29/0085 1",
MinguoChronology.INSTANCE));
System.out.printf("%s%n", StringConverter.fromString("10/29/2539 B.E.",
ThaiBuddhistChronology.INSTANCE));
System.out.printf("%s%n", StringConverter.fromString("6/16/1417 1",
HijrahChronology.INSTANCE));
打印的字符串应全部转换回 1996 年 10 月 29 日:
1996-10-29
1996-10-29
1996-10-29
1996-10-29