Format date in yyyy-MM-dd hh:mm:ss format from whatever format

问题

I am having various date String and want to format in particular format using java

String arr[] = {"Jul 02,2020 ","15-10-2015 10:20:56","2015/10/26 12:10:39","27-04-2016 10:22:56","April 7, 2020"};
    Arrays.asList(arr).forEach(date->{
        try {
            System.out.println(convertDate(date, "yyyy-MM-dd hh:mm:ss"));
        } catch (ParseException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    });

public static String getDateString(String date,String patternStr) throws ParseException {
    if(StringUtils.isNotEmpty(date)&& StringUtils.isNotEmpty(patternStr)) {
        SimpleDateFormat pattern = new SimpleDateFormat(patternStr);
        Date dateObject =new Date(date);
        return pattern.format(dateObject).toString();
    }
    return date;
}

But i am getting parse Exception for some of the date value.Is there any generic way to support for all the input date value .

回答1:

I recommend you switch from the outdated and error-prone java.util date-time API to the rich set of modern date-time API. Using DateTimeFormatterBuilder, you can build a format including all expected date-time formats and hour, minute, second defaulting to 0.

Demo

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.time.format.DateTimeFormatterBuilder;
import java.time.temporal.ChronoField;

public class Main {
    public static void main(final String[] args) {
        String arr[] = { "Jul 02,2020 ", "15-10-2015 10:20:56", "2015/10/26 12:10:39", "27-04-2016 10:22:56",
                "April 7, 2020" };
        DateTimeFormatter formatter = new DateTimeFormatterBuilder()
                                        .appendPattern("[MMM d,yyyy]")
                                        .appendPattern("[dd-MM-yyyy HH:mm:ss]")
                                        .appendPattern("[yyyy/MM/dd HH:mm:ss]")
                                        .appendPattern("[dd-MM-yyyy HH:mm:ss]")
                                        .appendPattern("[MMMM d, yyyy]")
                                        .parseDefaulting(ChronoField.HOUR_OF_DAY, 0)
                                        .parseDefaulting(ChronoField.MINUTE_OF_HOUR, 0)
                                        .parseDefaulting(ChronoField.SECOND_OF_MINUTE, 0)
                                        .toFormatter();

        for (String s : arr) {
            LocalDateTime ldt = LocalDateTime.parse(s.trim(), formatter);
            System.out.println("LocalDate#toString: " + ldt + ", " + "Formatted: "
                    + ldt.format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss")));
        }
    }
}

Output:

LocalDate#toString: 2020-07-02T00:00, Formatted: 2020-07-02 00:00:00
LocalDate#toString: 2015-10-15T10:20:56, Formatted: 2015-10-15 10:20:56
LocalDate#toString: 2015-10-26T12:10:39, Formatted: 2015-10-26 12:10:39
LocalDate#toString: 2016-04-27T10:22:56, Formatted: 2016-04-27 10:22:56
LocalDate#toString: 2020-04-07T00:00, Formatted: 2020-04-07 00:00:00

回答2:

No way you can do that. For every Date string , you need to pass the pattern along with it. Else you have to build your own String parser which can be ugly and cumbersome.

First of all the constructor accepting String is deprecated as of JDK version 1.1, replaced by DateFormat.parse(String s).

Check the doc

The right way to parse date from string is:

String sDate1="31/12/1998";  
Date date1=new SimpleDateFormat("dd/MM/yyyy").parse(sDate1);

来源：https://stackoverflow.com/questions/62708324/format-date-in-yyyy-mm-dd-hhmmss-format-from-whatever-format