How to get the given date string format(pattern) i

Question

I want to get the format of a given date string.

Example: I have a string like 2011-09-27T07:04:21.97-05:00 and the date format of this string is yyyy-MM-dd'T'HH:mm:ss.SSS.

Here I want to find out this date format when I pass string(2011-09-27T07:04:21.97-05:00) to a method which will return the format(yyyy-MM-dd'T'HH:mm:ss.SSS), then later I will format my given date string according to my requirement(like yy-mm--dd or mm/dd/yyyy).

Can any one tell me how can I get it achieved?

Answer 1

If I understand you correctly, you want to parse arbitrary strings (that is, string of a format you don't know) as dates by using DateFormat.parse()? Then you have to deal with issues like how to handle 01-02-03 (2 Jan 2003? 1 Feb 2003? etc.)

You should know at least something about the expected format, like a choice of several predefined formats for your input.

Answer 2

You could try dateparser.

It can recognize any String automatically, and parse it into Date, Calendar, LocalDateTime, OffsetDateTime correctly and quickly(1us~1.5us).

It doesn't based on any natural language analyzer or SimpleDateFormat or regex.Pattern.

With it, you don't have to prepare any appropriate patterns like yyyy-MM-dd'T'HH:mm:ss'Z' or MM/dd/yyyy HH:mm:ss etc:

Date date = DateParserUtils.parseDate("2015-04-29T10:15:00.500+0000");
Calendar calendar = DateParserUtils.parseCalendar("2015-04-29T10:15:00.500Z");
LocalDateTime dateTime = DateParserUtils.parseDateTime("2015-04-29 10:15:00.500 +00:00");

And it has better performance than loop-try multiple SimpleDateFormat.

Please enjoy it.

Answer 3

I think you should try to parse input string with some predefine patterns. The one that works is the one you need. Remember that some patterns are quite tricky.

01.12.12 is 01 December 2012 in Europe but 12 January 2012 in USA. It could be 12 December 2001 too.

Answer 4

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class NewClass {

    private static final String[] formats = { 
                "yyyy-MM-dd'T'HH:mm:ss'Z'",   "yyyy-MM-dd'T'HH:mm:ssZ",
                "yyyy-MM-dd'T'HH:mm:ss",      "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'",
                "yyyy-MM-dd'T'HH:mm:ss.SSSZ", "yyyy-MM-dd HH:mm:ss", 
                "MM/dd/yyyy HH:mm:ss",        "MM/dd/yyyy'T'HH:mm:ss.SSS'Z'", 
                "MM/dd/yyyy'T'HH:mm:ss.SSSZ", "MM/dd/yyyy'T'HH:mm:ss.SSS", 
                "MM/dd/yyyy'T'HH:mm:ssZ",     "MM/dd/yyyy'T'HH:mm:ss", 
                "yyyy:MM:dd HH:mm:ss",        "yyyyMMdd", };

        /*
         * @param args
         */
    public static void main(String[] args) {
        String yyyyMMdd = "20110917";   
        parse(yyyyMMdd);
    }

    public static void parse(String d) {
        if (d != null) {
            for (String parse : formats) {
                SimpleDateFormat sdf = new SimpleDateFormat(parse);
                try {
                    sdf.parse(d);
                    System.out.println("Printing the value of " + parse);
                } catch (ParseException e) {

                }
            }
        }
    }
}

Answer 5

you can do like this way, I don't know good way or not but try this

first create the SimpleDateFormat object

SimpleDateFormt sdf = new SimpleDateFormat("yyyy-MM-dd 'T' HH:mm:ss.SSS");

now when check the date if this will parse in this format then change as per your format

try{
     Date date = sdf.parse(yourdate);
     sdf.applyPattern("yy-mm--dd or mm/dd/yyyy");
     String dateformat = sdf.format(date);
}catch(Exception ex) { // here forgot the exact exception class Parse exception was used
    // do something here
}

updated post:

Returning a date format from an unknown format of date string in java

How to convert String to Date without knowing the format?

Parse any date in Java

Answer 6

You will need to take the inital date string and covert it to a date object and pass that converted date object and format it to your required string.