java - 如何将具有不同模式的星期名称解析为 DayOfWeek？

Question

我需要将工作日名称解析为 DayOfWeek。工作日名称可以是短格式('Mon')或长格式('Monday')。

目前我想出了这样的解决方案:

DateTimeFormatter dtf = DateTimeFormatter.ofPattern("EEE", locale);
DayOfWeek dayOfWeek;
try {
    dayOfWeek = DayOfWeek.from(dtf.parse(value));
}
catch (DateTimeException e) {
    dtf = DateTimeFormatter.ofPattern("EEEE", locale);
    dayOfWeek = DayOfWeek.from(dtf.parse(value));
}

有更短的解决方案吗？

Answer 1

您可以将 DateTimeFormatterBuilder 与可选模式一起使用。这些将按照您附加它们的顺序进行尝试。如果所有模式都失败，仍会抛出 DateTimeException。

final DateTimeFormatter dtf = new DateTimeFormatterBuilder()
        .appendOptional(DateTimeFormatter.ofPattern("EEEE"))
        .appendOptional(DateTimeFormatter.ofPattern("E"))
        .toFormatter(locale);

final DayOfWeek dow1 = DayOfWeek.from(dtf.parse("Mon"));
final DayOfWeek dow2 = DayOfWeek.from(dtf.parse("Monday"));

请注意，如果您愿意，结果 DayOfWeek 现在可以是最终的。

---

尝试跨多种语言(多个语言环境)使用相同的代码。

for ( final Locale locale : new Locale[] { Locale.US , Locale.CANADA_FRENCH , Locale.ITALY , Locale.KOREA } ) {
    final String inputShort = ( DayOfWeek.MONDAY.getDisplayName ( TextStyle.SHORT, locale ) );
    final String inputFull = ( DayOfWeek.MONDAY.getDisplayName ( TextStyle.FULL, locale ) );

    final DateTimeFormatter dtf = new DateTimeFormatterBuilder ( )
            .appendOptional ( DateTimeFormatter.ofPattern ( "EEEE" ) )
            .appendOptional ( DateTimeFormatter.ofPattern ( "E" ) )
            .toFormatter ( locale );

    final DayOfWeek dow1 = DayOfWeek.from ( dtf.parse ( inputShort ) ); 
    final DayOfWeek dow2 = DayOfWeek.from ( dtf.parse ( inputFull ) ); 

    System.out.println ( "" );
    System.out.println ( "Language: " + locale.getDisplayLanguage ( Locale.US ) );
    System.out.println ( "inputShort: " + inputShort + " | dow1: " + dow1 );
    System.out.println ( "inputFull: " + inputFull + " | dow2: " + dow2 );
}

运行时。

Language: English
inputShort: Mon | dow1: MONDAY
inputFull: Monday | dow2: MONDAY

Language: French
inputShort: lun. | dow1: MONDAY
inputFull: lundi | dow2: MONDAY

Language: Italian
inputShort: lun | dow1: MONDAY
inputFull: lunedì | dow2: MONDAY

Locale: Korean
inputShort: 월 | dow1: MONDAY
inputFull: 월요일 | dow2: MONDAY