我正在使用新的日期时间 API,但运行时:
public class Test {
public static void main(String[] args){
String dateFormatted = LocalDate.now()
.format(DateTimeFormatter
.ofPattern("yyyy-MM-dd HH:mm:ss"));
System.out.println(dateFormatted);
}
}
它抛出:
Exception in thread "main" java.time.temporal.UnsupportedTemporalTypeException: Unsupported field: HourOfDay
at java.time.LocalDate.get0(LocalDate.java:680)
at java.time.LocalDate.getLong(LocalDate.java:659)
at java.time.format.DateTimePrintContext.getValue(DateTimePrintContext.java:298)
at java.time.format.DateTimeFormatterBuilder$NumberPrinterParser.format(DateTimeFormatterBuilder.java:2543)
at java.time.format.DateTimeFormatterBuilder$CompositePrinterParser.format(DateTimeFormatterBuilder.java:2182)
at java.time.format.DateTimeFormatter.formatTo(DateTimeFormatter.java:1745)
at java.time.format.DateTimeFormatter.format(DateTimeFormatter.java:1719)
at java.time.LocalDate.format(LocalDate.java:1685)
at Test.main(Test.java:23)
当查看 LocalDate 类的源代码时,我看到:
private int get0(TemporalField field) {
switch ((ChronoField) field) {
case DAY_OF_WEEK: return getDayOfWeek().getValue();
case ALIGNED_DAY_OF_WEEK_IN_MONTH: return ((day - 1) % 7) + 1;
case ALIGNED_DAY_OF_WEEK_IN_YEAR: return ((getDayOfYear() - 1) % 7) + 1;
case DAY_OF_MONTH: return day;
case DAY_OF_YEAR: return getDayOfYear();
case EPOCH_DAY: throw new UnsupportedTemporalTypeException("Invalid field 'EpochDay' for get() method, use getLong() instead");
case ALIGNED_WEEK_OF_MONTH: return ((day - 1) / 7) + 1;
case ALIGNED_WEEK_OF_YEAR: return ((getDayOfYear() - 1) / 7) + 1;
case MONTH_OF_YEAR: return month;
case PROLEPTIC_MONTH: throw new UnsupportedTemporalTypeException("Invalid field 'ProlepticMonth' for get() method, use getLong() instead");
case YEAR_OF_ERA: return (year >= 1 ? year : 1 - year);
case YEAR: return year;
case ERA: return (year >= 1 ? 1 : 0);
}
throw new UnsupportedTemporalTypeException("Unsupported field: " + field);
}
正如文档中所述:
此方法将创建一个基于简单模式的格式化程序
类文档中描述的字母和符号。
所有这些字母都是defined http://docs.oracle.com/javase/8/docs/api/java/time/format/DateTimeFormatter.html#patterns.
So why DateTimeFormatter.ofPattern
不允许我们使用一些模式字母?
LocalDate
仅表示日期,而不是日期时间。所以“HH:mm:ss”在格式化时没有意义LocalDate
. Use a LocalDateTime
相反,假设您想同时表示日期和时间。
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