2021-04-18 11:35  阅读(54)
文章分类:Java 基础教程 文章标签:JavaJava 教程
©  原文作者:w3cschool 原文地址:https://www.w3cschool.cn/java/java-date-time-methods.html

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。

2021041811316_1.png

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。

2021041811315_2.png

例3

以下代码显示如何将日期转换为不同的日期系统。

    /*
     * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
     *
     * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     *
     *   - Redistributions of source code must retain the above copyright
     *     notice, this list of conditions and the following disclaimer.
     *
     *   - Redistributions in binary form must reproduce the above copyright
     *     notice, this list of conditions and the following disclaimer in the
     *     documentation and/or other materials provided with the distribution.
     *
     *   - Neither the name of Oracle or the names of its
     *     contributors may be used to endorse or promote products derived
     *     from this software without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
     * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
     * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
     * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
     * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
     * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
     * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
     * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
     * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
     * 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。

2021041811315_3.png

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