Java 非ISO日历系统

Java日期时间 - Java非ISO日历系统

LocalDate使用ISO日历系统，这是公历。

Java Date-Time API还支持其他日历，例如泰国佛教日历，Hijrah日历，Minguo日历和日历。

非ISO日历相关类在java.time.chrono包中定义。

对于每个可用的非ISO日历系统，有一个自定义的年表和自定义的Date类。

自定义的Chronology类表示日历系统，而自定义的Date类表示自定义日历系统中的日期。

每个自定义Chronology类都包含一个INSTANCE常量，表示该类的单例实例。

例子

以下代码显示获取泰国佛教日历中的当前日期：

import java.time.chrono.ThaiBuddhistChronology;
import java.time.chrono.ThaiBuddhistDate;

public class Main {

  public static void main(String[] args) {
    ThaiBuddhistChronology thaiBuddhistChrono = ThaiBuddhistChronology.INSTANCE;
    ThaiBuddhistDate now = thaiBuddhistChrono.dateNow();
    ThaiBuddhistDate now2 = ThaiBuddhistDate.now();
    System.out.println("Current Date  in Thai  Buddhist: " + now);
    System.out.println("Current Date  in Thai  Buddhist: " + now2);
  }
}

上面的代码生成以下结果。

例2

我们可以使用 from()方法将日历系统中的日期转换为另一个日历系统。

以下代码显示如何将ISO日期转换为泰语佛教日期，反之亦然。

import java.time.LocalDate;
import java.time.chrono.ThaiBuddhistDate;

public class Main {

  public static void main(String[] args) {
    ThaiBuddhistDate thaiBuddhistNow = ThaiBuddhistDate.now();
    LocalDate isoNow = LocalDate.now();
    System.out.println("Thai  Buddhist Current Date: " + thaiBuddhistNow);
    System.out.println("ISO  Current Date: " + isoNow);

    // Convert Thai Buddhist date to ISO date and vice versa
    ThaiBuddhistDate thaiBuddhistNow2 = ThaiBuddhistDate.from(isoNow);
    LocalDate isoNow2 = LocalDate.from(thaiBuddhistNow);
    System.out.println("Thai  Buddhist Current Date  from  ISO:  "
        + thaiBuddhistNow2);
    System.out.println("ISO  Current Date  from  Thai  Buddhist: " + isoNow2);

  }
}

上面的代码生成以下结果。

例3

以下代码显示如何将日期转换为不同的日期系统。

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 */
import java.time.*;
import java.time.chrono.*;
import java.time.format.*;
import java.time.temporal.*;
import java.util.Locale;
import java.io.PrintStream;

/*
 * Convert LocalDate -> ChronoLocalDate -> String and back.
 */

public class Main {

  /**
   * 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;
      }
      String pattern = "M/d/yyyy GGGGG";
      DateTimeFormatter dateFormatter = DateTimeFormatter.ofPattern(pattern);
      return dateFormatter.format(cDate);
    } else {
      return "";
    }
  }

  /**
   * 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;
  }

  public static void main(String[] args) {
    LocalDate date = LocalDate.of(1996, Month.OCTOBER, 29);
    System.out.printf("%s%n", toString(date, JapaneseChronology.INSTANCE));
    System.out.printf("%s%n", toString(date, MinguoChronology.INSTANCE));
    System.out.printf("%s%n", toString(date, ThaiBuddhistChronology.INSTANCE));
    System.out.printf("%s%n", toString(date, HijrahChronology.INSTANCE));

    System.out.printf("%s%n",
        fromString("10/29/0008 H", JapaneseChronology.INSTANCE));
    System.out.printf("%s%n",
        fromString("10/29/0085 1", MinguoChronology.INSTANCE));
    System.out.printf("%s%n",
        fromString("10/29/2539 B.E.", ThaiBuddhistChronology.INSTANCE));
    System.out.printf("%s%n",
        fromString("6/16/1417 1", HijrahChronology.INSTANCE));
  }
}

上面的代码生成以下结果。