Convert date to given format is not working

Question

I am trying to convert date from one format to another using formatter. But somehow this does not see to be working.

Following is my code

Date today = Calendar.getInstance().getTime();
SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss.ms");
String folderName = formatter.format(today); 
Date date = formatter.parse(folderName);
System.out.println("Folder date = " + date); //This prints Wed Nov 09 06:05:57 IST 2016

I need date to be printed in yyyy-MM-dd hh:mm:ss.ms format. That is I need it to be 2016-11-09 06:50:25.5025 and not Wed Nov 09 06:05:57 IST 2016 In folderName it is in correct format but when I convert back to date again format changes. Could you please let me know what I am missing?

"ms" ?? try "SSS" ! See https://docs.oracle.com/javase/8/docs/api/java/text/SimpleDateFormat.html — Fildor, Nov 09 '16 at 13:17
FYI, the troublesome old date-time classes such as [`java.util.Date`](https://docs.oracle.com/javase/8/docs/api/java/util/Date.html), [`java.util.Calendar`](https://docs.oracle.com/javase/8/docs/api/java/util/Calendar.html), and `java.text.SimpleTextFormat` are now [legacy](https://en.wikipedia.org/wiki/Legacy_system), supplanted by the [java.time](https://docs.oracle.com/javase/8/docs/api/java/time/package-summary.html) classes. See [Tutorial by Oracle](https://docs.oracle.com/javase/tutorial/datetime/TOC.html). — Basil Bourque, Jun 18 '17 at 00:53

score 3 · Answer 1 · answered Nov 09 '16 at 13:21

3

You did two errors:

The format (check here for a complete list of formats) is yyyy-MM-dd hh:mm:ss.SSS

And you need to print the String, not the Date.

Date today = Calendar.getInstance().getTime();
SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss.SSS");
String folderName = formatter.format(today); 
System.out.println("Folder date = " + folderName);

answered Nov 09 '16 at 13:21

Davide Lorenzo MARINO

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When I print it that way it works. But I need date object to hold that format. Is it possible? – Sachin Nov 09 '16 at 13:22
1

@Sachin Date object **has no format**. That's what formatters are for. – Fildor Nov 09 '16 at 13:22
Date holds the value, not the format. If you need to print it you need to convert it to a string using a DateFormat as you did. – Davide Lorenzo MARINO Nov 09 '16 at 13:23

score 1 · Answer 2 · answered Jun 18 '17 at 01:02

Using java.time

You are using troublesome old date-time classes, now legacy, supplanted by the java.time classes.

ZoneId z = ZoneId.of( "Asia/Kolkata" ) ;
ZonedDateTime now = ZonedDateTime.now( z ) ;

now.toString(): 2016-11-09T06:50:25.502+05:30[Asia/Kolkata]

Generate a string. Your desired format is close to standard ISO 8601 format, just replace the T in the middle with a space. The java.time classes know about ISO 8601 formats.

DateTimeFormatter f = DateTimeFormatter.ISO_LOCAL_DATE_TIME ;
String output = now.format( f ).replace( "T" , " " ) ;

2016-11-09 06:50:25.502

About java.time

The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.

The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.

To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.

Where to obtain the java.time classes?

Java SE 8, Java SE 9, and later
- Built-in.
- Part of the standard Java API with a bundled implementation.
- Java 9 adds some minor features and fixes.
Java SE 6 and Java SE 7
- Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
Android
- The ThreeTenABP project adapts ThreeTen-Backport (mentioned above) for Android specifically.
- See How to use ThreeTenABP….

The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.

Convert date to given format is not working

2 Answers2

Using java.time

About java.time