报错:Unsupported field: HourOfDay

报错:Unsupported field: HourOfDay

这个错误就比较搞笑也比较低级了.

代码以下

LocalDate now = LocalDate.now();
String year = now.format(DateTimeFormatter.ofPattern("yyyy"));
String hour = now.format(DateTimeFormatter.ofPattern("MM-dd-HH"));

报错以下

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$NumberPrinterParser.format(DateTimeFormatterBuilder.java:2540)
    at java.time.format.DateTimeFormatterBuilder$CompositePrinterParser.format(DateTimeFormatterBuilder.java:2179)
    at java.time.format.DateTimeFormatter.formatTo(DateTimeFormatter.java:1746)
    at java.time.format.DateTimeFormatter.format(DateTimeFormatter.java:1720)
    at java.time.LocalDate.format(LocalDate.java:1691)
    at com.feiyangshop.recommendation.HdfsHandler.main(HdfsHandler.java:21)

我还追踪到了jdk源码中查看.

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);
    }

最后把异常抛出的代码在这.

说明我在now.format(DateTimeFormatter.ofPattern("MM-dd-HH"));的HH是不在case之中的.

为何case中只有年月日,没有小时和分秒呢?

emmmmm.

答案就是:我用错类了

应该使用LocalDateTime这个类.这个类包含时分秒.

LocalDateTime now = LocalDateTime.now();
String year = now.format(DateTimeFormatter.ofPattern("yyyy"));
String hour = now.format(DateTimeFormatter.ofPattern("MM-dd-HH"));

FIN