惠州​​如何将日期转换为不同的Java日期系统？_北大青鸟IT学校

如何将日期转换为不同的Java日期系统？相信学过Java的同学都遇到过这个问题，那么答案是什么呢？接下来一起来看看惠州北大青鸟老师是怎么回答的。

实例

以下代码显示如何将日期转换为不同的Java日期系统。

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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/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。

10/29/0008 H

10/29/0085 1

10/29/2539 B.E.

6/16/1417 1

1996-10-29

1996-10-29

1996-10-29

1996-10-29

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