转换日期格式：Java中的转换错误？

Question

I am trying to convert this date to a different format. unfortuantely havnt been successful parsing the date and retaining all the information correctly.

06-Dec-2017 07:14:56.656PM to 2017-12-06 19:14:56.656

If I try to parse the input date

LocalDateTime.parse("06-Dec-2017 07:14:56.656PM",
        DateTimeFormatter.ofPattern("D-MMM-yyyy HH:mm:ss.SSSa"));

I get the following error - not sure what it means?

Exception in thread "main" java.time.format.DateTimeParseException: Text '06-Dec-2017 07:14:56.656PM' could not be parsed: Conflict found: Field MonthOfYear 1 differs from MonthOfYear 12 derived from 2017-01-06
    at java.time.format.DateTimeFormatter.createError(Unknown Source)
    at java.time.format.DateTimeFormatter.parse(Unknown Source)
    at java.time.LocalDateTime.parse(Unknown Source)
    at com.cordys.coe.alf.logger.DBLogger.main(DBLogger.java:366)
Caused by: java.time.DateTimeException: Conflict found: Field MonthOfYear 1 differs from MonthOfYear 12 derived from 2017-01-06
    at java.time.format.Parsed.crossCheck(Unknown Source)
    at java.time.format.Parsed.crossCheck(Unknown Source)

and if try

System.out.println(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss:SSS")
        .format((new SimpleDateFormat("DD-MMM-yyyy HH:mm:ss.SSSa")
                .parse("06-Dec-2017 07:14:56.656PM"))));

It give the following which is confusing, and probably not correct. 2017-01-06 07:14:56:656

Answer 1

You have 2 problems

1. D should be d

D represents day of year

d represents day-of-month

2. HH should be hh

H represents hour-of-day (0-23)

h represents clock-hour-of-am-pm (1-12)

Please change D-MMM-yyyy HH:mm:ss.SSSa to d-MMM-yyyy hh:mm:ss.SSSa

For more information , check the oracle docs