Develop Reference

Get day, month and year separately using SimpleDateFormat

I have a SimleDateFormat like this
SimpleDateFormat format = new SimpleDateFormat("MMM dd,yyyy hh:mm");
String date = format.format(Date.parse(payback.creationDate.date));
I'm giving date with the format like "Jan,23,2014".
Now, I want to get day, month and year separately. How can I implement this?

If you need to get the values separately, then use more than one SimpleDateFormat.
SimpleDateFormat dayFormat = new SimpleDateFormat("dd");
String day = dayFormat.format(Date.parse(payback.creationDate.date));
SimpleDateFormat monthFormat = new SimpleDateFormat("MM");
String month = monthFormat .format(Date.parse(payback.creationDate.date));
etc.

SimpleDateFormat format = new SimpleDateFormat("MMM dd,yyyy hh:mm", Locale.ENGLISH);
Date theDate = format.parse("JAN 13,2014 09:15");
Calendar myCal = new GregorianCalendar();
myCal.setTime(theDate);
System.out.println("Day: " + myCal.get(Calendar.DAY_OF_MONTH));
System.out.println("Month: " + myCal.get(Calendar.MONTH) + 1);
System.out.println("Year: " + myCal.get(Calendar.YEAR));

Wow, SimpleDateFormat for getting string parts? It can be solved much easier if your input string is like "Jan,23,2014":
String input = "Jan,23,2014";
String[] out = input.split(",");
System.out.println("Year = " + out[2]);
System.out.println("Month = " + out[0]);
System.out.println("Day = " + out[1]);
Output:
Year = 2014
Month = Jan
Day = 23
But if you really want to use SimpleDateFormat because of some reason, the solution will be the following:
String input = "Jan,23,2014";
SimpleDateFormat format = new SimpleDateFormat("MMM,dd,yyyy");
Date date = format.parse(input);
Calendar calendar = Calendar.getInstance(TimeZone.getDefault());
calendar.setTime(date);
System.out.println(calendar.get(Calendar.YEAR));
System.out.println(calendar.get(Calendar.DAY_OF_MONTH));
System.out.println(new SimpleDateFormat("MMM").format(calendar.getTime()));
Output:
2014
23
Jan

The accepted answer here suggests to use more than one SimpleDateFormat, but it's possible to do this using one SimpleDateFormat instance and calling applyPattern.
Note: I believe this post would also be helpful for those who were searching for setPattern() just like me.
Date date=new Date();
SimpleDateFormat simpleDateFormat = new SimpleDateFormat();
simpleDateFormat.applyPattern("dd");
System.out.println("Day : " + simpleDateFormat.format(date));
simpleDateFormat.applyPattern("MMM");
System.out.println("Month : " + simpleDateFormat.format(date));
simpleDateFormat.applyPattern("yyyy");
System.out.println("Year : " + simpleDateFormat.format(date));

tl;dr
Use LocalDate class.
LocalDate
.parse(
"Jan,23,2014" ,
DateTimeFormatter.ofPattern( "MMM,dd,uuuu" , Locale.US )
)
.getYear()
… or .getMonthValue() or .getDayOfMonth.
java.time
The other Answers use outmoded classes. The java.time classes supplant those troublesome old legacy classes.
LocalDate
The LocalDate class represents a date-only value without time-of-day and without time zone.
String input = "Jan,23,2014";
DateTimeFormatter f = DateTimeFormatter.ofPattern( "MMM,d,uuuu" );
LocalDate ld = LocalDate.parse( input , f );
Interrogate for the parts you want.
int year = ld.getYear();
int month = ld.getMonthValue();
int dayOfMonth = ld.getDayOfMonth();
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.
You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes.
Where to obtain the java.time classes?
Java SE 8, Java SE 9, Java SE 10, Java SE 11, and later - 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
Most of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
Android
Later versions of Android bundle implementations of the java.time classes.
For earlier Android (<26), the ThreeTenABP project adapts ThreeTen-Backport (mentioned above). 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.

Use this to parse "Jan,23,2014"
SimpleDateFormat fmt = new SimpleDateFormat("MMM','dd','yyyy");
Date dt = fmt.parse("Jan,23,2014");
then you can get whatever part of the date.

Are you accepting this ?
int day = 25 ; //25
int month =12; //12
int year = 1988; // 1988
Calendar c = Calendar.getInstance();
c.set(year, month-1, day, 0, 0);
SimpleDateFormat format = new SimpleDateFormat("MMM dd,yyyy hh:mm");
System.out.println(format.format(c.getTime()));
Display as Dec 25,1988 12:00
UPDATE : based on Comment
DateFormat format = new SimpleDateFormat("MMM");
System.out.println(format.format(format.parse("Jan,23,2014")));
NOTE: Date.parse() is #deprecated and as per API it is recommend to use DateFormat.parse

public static String getDate(long milliSeconds, String dateFormat) {
// Create a DateFormatter object for displaying date in specified
// format.
SimpleDateFormat formatter = new SimpleDateFormat(dateFormat,
Locale.getDefault());
// Create a calendar object that will convert the date and time value in
// milliseconds to date.
Calendar calendar = Calendar.getInstance();
calendar.setTimeInMillis(milliSeconds);
return formatter.format(calendar.getTime());
}

How do I convert the date from one format to another date object in another format without using any deprecated classes?

I'd like to convert a date in date1 format to a date object in date2 format.
SimpleDateFormat simpleDateFormat = new SimpleDateFormat("MMMM dd, yyyy");
SimpleDateFormat simpleDateFormat1 = new SimpleDateFormat("yyyyMMdd");
Calendar cal = Calendar.getInstance();
cal.set(2012, 8, 21);
Date date = cal.getTime();
Date date1 = simpleDateFormat.parse(date);
Date date2 = simpleDateFormat.parse(date1);
println date1
println date2

Use SimpleDateFormat#format:
DateFormat originalFormat = new SimpleDateFormat("MMMM dd, yyyy", Locale.ENGLISH);
DateFormat targetFormat = new SimpleDateFormat("yyyyMMdd");
Date date = originalFormat.parse("August 21, 2012");
String formattedDate = targetFormat.format(date); // 20120821
Also note that parse takes a String, not a Date object, which is already parsed.

tl;dr
LocalDate.parse(
"January 08, 2017" ,
DateTimeFormatter.ofPattern( "MMMM dd, uuuu" , Locale.US )
).format( DateTimeFormatter.BASIC_ISO_DATE )
Using java.time
The Question and other Answers use troublesome old date-time classes, now legacy, supplanted by the java.time classes.
You have date-only values, so use a date-only class. The LocalDate class represents a date-only value without time-of-day and without time zone.
String input = "January 08, 2017";
Locale l = Locale.US ;
DateTimeFormatter f = DateTimeFormatter.ofPattern( "MMMM dd, uuuu" , l );
LocalDate ld = LocalDate.parse( input , f );
Your desired output format is defined by the ISO 8601 standard. For a date-only value, the “expanded” format is YYYY-MM-DD such as 2017-01-08 and the “basic” format that minimizes the use of delimiters is YYYYMMDD such as 20170108.
I strongly suggest using the expanded format for readability. But if you insist on the basic format, that formatter is predefined as a constant on the DateTimeFormatter class named BASIC_ISO_DATE.
String output = ld.format( DateTimeFormatter.BASIC_ISO_DATE );
See this code run live at IdeOne.com.
ld.toString(): 2017-01-08
output: 20170108
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.
To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.
The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.
You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes. Hibernate 5 & JPA 2.2 support java.time.
Where to obtain the java.time classes?
Java SE 8, Java SE 9, Java SE 10, Java SE 11, and later - Part of the standard Java API with a bundled implementation.
Java 9 brought some minor features and fixes.
Java SE 6 and Java SE 7
Most of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
Android
Later versions of Android (26+) bundle implementations of the java.time classes.
For earlier Android (<26), the process of API desugaring brings a subset of the java.time functionality not originally built into Android.
If the desugaring does not offer what you need, the ThreeTenABP project adapts ThreeTen-Backport (mentioned above) to Android. See How to use ThreeTenABP….

Since Java 8, we can achieve this as follows:
private static String convertDate(String strDate)
{
//for strdate = 2017 July 25
DateTimeFormatter f = new DateTimeFormatterBuilder().appendPattern("yyyy MMMM dd")
.toFormatter();
LocalDate parsedDate = LocalDate.parse(strDate, f);
DateTimeFormatter f2 = DateTimeFormatter.ofPattern("MM/d/yyyy");
String newDate = parsedDate.format(f2);
return newDate;
}
The output will be : "07/25/2017"

Try this
This is the simplest way of changing one date format to another
public String changeDateFormatFromAnother(String date){
#SuppressLint("SimpleDateFormat") DateFormat inputFormat = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
#SuppressLint("SimpleDateFormat") DateFormat outputFormat = new SimpleDateFormat("dd MMMM yyyy");
String resultDate = "";
try {
resultDate=outputFormat.format(inputFormat.parse(date));
} catch (ParseException e) {
e.printStackTrace();
}
return resultDate;
}

Kotlin equivalent of answer answered by João Silva
fun getFormattedDate(originalFormat: SimpleDateFormat, targetFormat: SimpleDateFormat, inputDate: String): String {
return targetFormat.format(originalFormat.parse(inputDate))
}
Usage (In Android):
getFormattedDate(
SimpleDateFormat(FormatUtils.d_MM_yyyy, Locale.getDefault()),
SimpleDateFormat(FormatUtils.d_MMM_yyyy, Locale.getDefault()),
dateOfTreatment
)
Note: Constant values:
// 25 Nov 2017
val d_MMM_yyyy = "d MMM yyyy"
// 25/10/2017
val d_MM_yyyy = "d/MM/yyyy"

Please refer to the following method. It takes your date String as argument1, you need to specify the existing format of the date
as argument2, and the result (expected) format as argument 3.
Refer to this link to understand various formats:
Available Date Formats
public static String formatDateFromOnetoAnother(String date,String givenformat,String resultformat) {
String result = "";
SimpleDateFormat sdf;
SimpleDateFormat sdf1;
try {
sdf = new SimpleDateFormat(givenformat);
sdf1 = new SimpleDateFormat(resultformat);
result = sdf1.format(sdf.parse(date));
}
catch(Exception e) {
e.printStackTrace();
return "";
}
finally {
sdf=null;
sdf1=null;
}
return result;
}

private String formatDate(String date, String inputFormat, String outputFormat) {
String newDate;
DateFormat inputDateFormat = new SimpleDateFormat(inputFormat);
inputDateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
DateFormat outputDateFormat = new SimpleDateFormat(outputFormat);
try {
newDate = outputDateFormat.format((inputDateFormat.parse(date)));
} catch (Exception e) {
newDate = "";
}
return newDate;
}

Hope this will help someone.
public static String getDate(
String date, String currentFormat, String expectedFormat)
throws ParseException {
// Validating if the supplied parameters is null
if (date == null || currentFormat == null || expectedFormat == null ) {
return null;
}
// Create SimpleDateFormat object with source string date format
SimpleDateFormat sourceDateFormat = new SimpleDateFormat(currentFormat);
// Parse the string into Date object
Date dateObj = sourceDateFormat.parse(date);
// Create SimpleDateFormat object with desired date format
SimpleDateFormat desiredDateFormat = new SimpleDateFormat(expectedFormat);
// Parse the date into another format
return desiredDateFormat.format(dateObj).toString();
}

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
String fromDateFormat = "dd/MM/yyyy";
String fromdate = 15/03/2018; //Take any date
String CheckFormat = "dd MMM yyyy";//take another format like dd/MMM/yyyy
String dateStringFrom;
Date DF = new Date();
try
{
//DateFormatdf = DateFormat.getDateInstance(DateFormat.SHORT);
DateFormat FromDF = new SimpleDateFormat(fromDateFormat);
FromDF.setLenient(false); // this is important!
Date FromDate = FromDF.parse(fromdate);
dateStringFrom = new
SimpleDateFormat(CheckFormat).format(FromDate);
DateFormat FromDF1 = new SimpleDateFormat(CheckFormat);
DF=FromDF1.parse(dateStringFrom);
System.out.println(dateStringFrom);
}
catch(Exception ex)
{
System.out.println("Date error");
}
output:- 15/03/2018
15 Mar 2018

//Convert input format 19-FEB-16 01.00.00.000000000 PM to 2016-02-19 01.00.000 PM
SimpleDateFormat inFormat = new SimpleDateFormat("dd-MMM-yy hh.mm.ss.SSSSSSSSS aaa");
Date today = new Date();
Date d1 = inFormat.parse("19-FEB-16 01.00.00.000000000 PM");
SimpleDateFormat outFormat = new SimpleDateFormat("yyyy-MM-dd hh.mm.ss.SSS aaa");
System.out.println("Out date ="+outFormat.format(d1));

convert date from "2009-12 Dec" format to "31-DEC-2009"

'2009-12 Dec' should be converted to '31-DEC-2009'
'2010-09 Sep' should be converted to '30-SEP-2010'
'2010-02 Feb' should be converted to '28-FEB-2010'
'2008-02 Feb' should be converted to '29-FEB-2008'
The values 2009-12 Dec, 2008-02 Feb will be displayed to the User in a drop down. The User have no option to select the DAY.
The user selected value should be passed to the Database. But the database expects the date in the format DD-MMM-YYYY. The query has '<= USER_DATE' condition. So, the last day of the month should be automatically selected and passed to the database.
Pl help me in writing the function that does the above job.
static SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM MMM");
public static String convertMapedToSqlFormat(final String maped) {
String convertedMaped = null;
//....
return convertedMaped;
}
#Test
public void testConvertMapedToSqlFormat() {
String[] mapedValues = { "2009-12 Dec", "2009-11 Nov", "2009-10 Oct",
"2009-09 Sep", "2009-08 Aug", "2009-07 Jul", "2009-06 Jun",
"2009-05 May", "2009-04 Apr", "2009-03 Mar", "2009-02 Feb",
"2009-01 Jan", "2008-12 Dec", "2008-11 Nov", "2008-10 Oct" };
for (String maped : mapedValues) {
System.out.println(convertMapedToSqlFormat(maped));
}
}

Convert it to Calendar and use Calendar#getActualMaximum() to obtain last day of month and set the day with it.
Kickoff example:
String oldString = "2009-12 Dec";
Calendar calendar = Calendar.getInstance();
calendar.setTime(new SimpleDateFormat("yyyy-MM").parse(oldString)); // Yes, month name is ignored but we don't need this.
calendar.set(Calendar.DATE, calendar.getActualMaximum(Calendar.DATE));
String newString = new SimpleDateFormat("dd-MMM-yyyy").format(calendar.getTime()).toUpperCase();
System.out.println(newString); // 31-DEC-2009

Use your DateFormat (but fix it to yyyy-dd MMM) to parse the date
convert the Date to Calendar
Use Calendar.getActualMaximim()
use dd-MMM-yyyy to format the obtained date.
call .toUpperCase()
So:
static SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM MMM");
static SimpleDateFormat dbDateFormat = new SimpleDateFormat("yyyy-MMM-dd");
public static String convertMapedToSqlFormat(final String maped) {
Date date = dateFormat.parse(mapped);
Calendar cal = Calendar.getInstance();
cal.setTime(date);
cal.set(Calendar.DAY_OF_MONTH, cal.getActualMaximum(Calendar.DAY_OF_MONTH));
return dbDateFormat.format(cal.getTime()).toUpperCase();
}
A few notes:
if possible use joda-time DateTime
avoid having strict date formats in the database.

Get the year and month from the YYYY-MM part of the string.
Use JODA to create a point in time corresponding to the first day of that month. Move one month forward, and one day backward. Flatten the time to the string representation you need.

Hi you have to parse your date,
like so
SimpleDateFormat df = new SimpleDateFormat("MM/dd/yyyy");
Date du = new Date();
du = df.parse(sDate);
df = new SimpleDateFormat("yyyy-MM-dd");
sDate = df.format(du);
Hope this helps.
Let me know if it does.
PK

java.time
Much easier now with the modern java.time classes that supplant the troublesome old date-time classes seen here in the Question and other Answers.
The java.time framework is built into Java 8 and later. These classes supplant the old troublesome date-time classes such as java.util.Date, .Calendar, & java.text.SimpleDateFormat.
Now in maintenance mode, the Joda-Time project also advises migration to java.time.
To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations.
Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport and further adapted to Android in ThreeTenABP.
The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time.
YearMonth
The YearMonth class provides just what you want.
YearMonth start = YearMonth.of( 2008 , Month.OCTOBER );
YearMonth stop = YearMonth.of( 2009 , Month.DECEMBER );
List<YearMonth> yms = new ArrayList<>();
YearMonth ym = start ;
while( ! ym.isAfter( stop ) ) {
yms.add( ym );
// Set up the next loop.
ym = ym.plusMonths( 1 );
}
To present, use a DateTimeFormatter to generate a String representation of the YearMonth value.
DateTimeFormatter f = DateTimeFormatter.ofPattern( "uuuu-MM MMM" );
f = f.withLocale( Locale.CANADA_FRENCH ); // Or Locale.US etc.
String output = ym.format( f );
To get the last day of the month, interrogate the YearMonth object.
LocalDate endOfMonth = ym.atEndOfMonth();
To present, use a DateTimeFormatter. Either let instantiate a formatter that automatically localizes appropriate to a specified Locale, or specify your own formatting pattern. Shown many times in many other Questions and Answers on Stack Overflow.

How to get the current time in YYYY-MM-DD HH:MI:Sec.Millisecond format in Java?

The code below gives me the current time. But it does not tell anything about milliseconds.
public static String getCurrentTimeStamp() {
SimpleDateFormat sdfDate = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");//dd/MM/yyyy
Date now = new Date();
String strDate = sdfDate.format(now);
return strDate;
}
I have a date in the format YYYY-MM-DD HH:MM:SS (2009-09-22 16:47:08).
But I want to retrieve the current time in the format YYYY-MM-DD HH:MM:SS.MS (2009-09-22 16:47:08.128, where 128 are the milliseconds).
SimpleTextFormat will work fine. Here the lowest unit of time is second, but how do I get millisecond as well?

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");

A Java one liner
public String getCurrentTimeStamp() {
return new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS").format(new Date());
}
in JDK8 style
public String getCurrentLocalDateTimeStamp() {
return LocalDateTime.now()
.format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSS"));
}

You only have to add the millisecond field in your date format string:
new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");
The API doc of SimpleDateFormat describes the format string in detail.

try this:-
http://docs.oracle.com/javase/6/docs/api/java/text/SimpleDateFormat.html
DateFormat dateFormat = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss.SSS");
Date date = new Date();
System.out.println(dateFormat.format(date));
or
DateFormat dateFormat = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
Calendar cal = Calendar.getInstance();
System.out.println(dateFormat.format(cal.getTime()));

tl;dr
Instant.now()
.toString()
2016-05-06T23:24:25.694Z
ZonedDateTime
.now
(
ZoneId.of( "America/Montreal" )
)
.format( DateTimeFormatter.ISO_LOCAL_DATE_TIME )
.replace( "T" , " " )
2016-05-06 19:24:25.694
java.time
In Java 8 and later, we have the java.time framework built into Java 8 and later. These new classes supplant the troublesome old java.util.Date/.Calendar classes. The new classes are inspired by the highly successful Joda-Time framework, intended as its successor, similar in concept but re-architected. Defined by JSR 310. Extended by the ThreeTen-Extra project. See the Tutorial.
Be aware that java.time is capable of nanosecond resolution (9 decimal places in fraction of second), versus the millisecond resolution (3 decimal places) of both java.util.Date & Joda-Time. So when formatting to display only 3 decimal places, you could be hiding data.
If you want to eliminate any microseconds or nanoseconds from your data, truncate.
Instant instant2 = instant.truncatedTo( ChronoUnit.MILLIS ) ;
The java.time classes use ISO 8601 format by default when parsing/generating strings. A Z at the end is short for Zulu, and means UTC.
An Instant represents a moment on the timeline in UTC with resolution of up to nanoseconds. Capturing the current moment in Java 8 is limited to milliseconds, with a new implementation in Java 9 capturing up to nanoseconds depending on your computer’s hardware clock’s abilities.
Instant instant = Instant.now (); // Current date-time in UTC.
String output = instant.toString ();
2016-05-06T23:24:25.694Z
Replace the T in the middle with a space, and the Z with nothing, to get your desired output.
String output = instant.toString ().replace ( "T" , " " ).replace( "Z" , "" ; // Replace 'T', delete 'Z'. I recommend leaving the `Z` or any other such [offset-from-UTC][7] or [time zone][7] indicator to make the meaning clear, but your choice of course.
2016-05-06 23:24:25.694
As you don't care about including the offset or time zone, make a "local" date-time unrelated to any particular locality.
String output = LocalDateTime.now ( ).toString ().replace ( "T", " " );
Joda-Time
The highly successful Joda-Time library was the inspiration for the java.time framework. Advisable to migrate to java.time when convenient.
The ISO 8601 format includes milliseconds, and is the default for the Joda-Time 2.4 library.
System.out.println( "Now: " + new DateTime ( DateTimeZone.UTC ) );
When run…
Now: 2013-11-26T20:25:12.014Z
Also, you can ask for the milliseconds fraction-of-a-second as a number, if needed:
int millisOfSecond = myDateTime.getMillisOfSecond ();

The easiest way was to (prior to Java 8) use,
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");
But SimpleDateFormat is not thread-safe. Neither java.util.Date. This will lead to leading to potential concurrency issues for users. And there are many problems in those existing designs. To overcome these now in Java 8 we have a separate package called java.time. This Java SE 8 Date and Time document has a good overview about it.
So in Java 8 something like below will do the trick (to format the current date/time),
LocalDateTime.now()
.format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSS"));
And one thing to note is it was developed with the help of the popular third party library joda-time,
The project has been led jointly by the author of Joda-Time (Stephen Colebourne) and Oracle, under JSR 310, and will appear in the new Java SE 8 package java.time.
But now the joda-time is becoming deprecated and asked the users to migrate to new java.time.
Note that from Java SE 8 onwards, users are asked to migrate to java.time (JSR-310) - a core part of the JDK which replaces this project
Anyway having said that,
If you have a Calendar instance you can use below to convert it to the new java.time,
Calendar calendar = Calendar.getInstance();
long longValue = calendar.getTimeInMillis();
LocalDateTime date =
LocalDateTime.ofInstant(Instant.ofEpochMilli(longValue), ZoneId.systemDefault());
String formattedString = date.format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSS"));
System.out.println(date.toString()); // 2018-03-06T15:56:53.634
System.out.println(formattedString); // 2018-03-06 15:56:53.634
If you had a Date object,
Date date = new Date();
long longValue2 = date.getTime();
LocalDateTime dateTime =
LocalDateTime.ofInstant(Instant.ofEpochMilli(longValue2), ZoneId.systemDefault());
String formattedString = dateTime.format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSS"));
System.out.println(dateTime.toString()); // 2018-03-06T15:59:30.278
System.out.println(formattedString); // 2018-03-06 15:59:30.278
If you just had the epoch milliseconds,
LocalDateTime date =
LocalDateTime.ofInstant(Instant.ofEpochMilli(epochLongValue), ZoneId.systemDefault());

I would use something like this:
String.format("%tF %<tT.%<tL", dateTime);
Variable dateTime could be any date and/or time value, see JavaDoc for Formatter.

I have a simple example here to display date and time with Millisecond......
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
public class MyClass{
public static void main(String[]args){
LocalDateTime myObj = LocalDateTime.now();
DateTimeFormatter myFormat = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSS");
String forDate = myObj.format(myFormat);
System.out.println("The Date and Time are: " + forDate);
}
}

To complement the above answers, here is a small working example of a program that prints the current time and date, including milliseconds.
import java.text.SimpleDateFormat;
import java.util.Date;
public class test {
public static void main(String argv[]){
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");
Date now = new Date();
String strDate = sdf.format(now);
System.out.println(strDate);
}
}

Use this to get your current time in specified format :
DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
System.out.print(dateFormat.format(System.currentTimeMillis())); }

java.time
The question and the accepted answer use java.util.Date and SimpleDateFormat which was the correct thing to do in 2009. In Mar 2014, the java.util date-time API and their formatting API, SimpleDateFormat were supplanted by the modern date-time API. Since then, it is highly recommended to stop using the legacy date-time API.
Solution using java.time, the modern date-time API:
LocalDateTime.now(ZoneId.systemDefault())
.format(DateTimeFormatter.ofPattern("uuuu-MM-dd HH:mm:ss.SSS"))
Some important points about this solution:
Replace ZoneId.systemDefault() with the applicable ZoneId e.g. ZoneId.of("America/New_York").
If the current date-time is required in the system's default timezone (ZoneId), you do not need to use LocalDateTime#now(ZoneId zone); instead, you can use LocalDateTime#now().
You can use y instead of u here but I prefer u to y.
Demo:
import java.time.LocalDateTime;
import java.time.ZoneId;
import java.time.format.DateTimeFormatter;
import java.util.Locale;
class Main {
public static void main(String args[]) {
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("uuuu-MM-dd HH:mm:ss.SSS", Locale.ENGLISH);
// Replace ZoneId.systemDefault() with the applicable ZoneId e.g.
// ZoneId.of("America/New_York")
LocalDateTime ldt = LocalDateTime.now(ZoneId.systemDefault());
String formattedDateTimeStr = ldt.format(formatter);
System.out.println(formattedDateTimeStr);
}
}
Output from a sample run in my system's timezone, Europe/London:
2023-01-02 09:53:14.353
ONLINE DEMO
Learn more about the modern Date-Time API from Trail: Date Time.

I don't see a reference to this:
SimpleDateFormat f = new SimpleDateFormat("yyyyMMddHHmmssSSS");
above format is also useful.
http://www.java2s.com/Tutorials/Java/Date/Date_Format/Format_date_in_yyyyMMddHHmmssSSS_format_in_Java.htm

Ans:
DateTimeFormatter dateFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSS");
ZonedDateTime start = Instant.now().atZone(ZoneId.systemDefault());
String startTimestamp = start.format(dateFormatter);

java.text (prior to java 8)
public static ThreadLocal<DateFormat> dateFormat = new ThreadLocal<DateFormat>() {
protected DateFormat initialValue() {
return new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");
};
};
...
dateFormat.get().format(new Date());
java.time
public static DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSS");
...
dateTimeFormatter.format(LocalDateTime.now());

The doc in Java 8 names it fraction-of-second , while in Java 6 was named millisecond. This brought me to confusion

You can simply get it in the format you want.
String date = String.valueOf(android.text.format.DateFormat.format("dd-MM-yyyy", new java.util.Date()));

Parse String to Date with Different Format in Java

I want to convert String to Date in different formats.
For example,
I am getting from user,
String fromDate = "19/05/2009"; // i.e. (dd/MM/yyyy) format
I want to convert this fromDate as a Date object of "yyyy-MM-dd" format
How can I do this?

Take a look at SimpleDateFormat. The code goes something like this:
SimpleDateFormat fromUser = new SimpleDateFormat("dd/MM/yyyy");
SimpleDateFormat myFormat = new SimpleDateFormat("yyyy-MM-dd");
try {
String reformattedStr = myFormat.format(fromUser.parse(inputString));
} catch (ParseException e) {
e.printStackTrace();
}

tl;dr
LocalDate.parse(
"19/05/2009" ,
DateTimeFormatter.ofPattern( "dd/MM/uuuu" )
)
Details
The other Answers with java.util.Date, java.sql.Date, and SimpleDateFormat are now outdated.
LocalDate
The modern way to do date-time is work with the java.time classes, specifically LocalDate. The LocalDate class represents a date-only value without time-of-day and without time zone.
DateTimeFormatter
To parse, or generate, a String representing a date-time value, use the DateTimeFormatter class.
DateTimeFormatter f = DateTimeFormatter.ofPattern( "dd/MM/uuuu" );
LocalDate ld = LocalDate.parse( "19/05/2009" , f );
Do not conflate a date-time object with a String representing its value. A date-time object has no format, while a String does. A date-time object, such as LocalDate, can generate a String to represent its internal value, but the date-time object and the String are separate distinct objects.
You can specify any custom format to generate a String. Or let java.time do the work of automatically localizing.
DateTimeFormatter f =
DateTimeFormatter.ofLocalizedDate( FormatStyle.FULL )
.withLocale( Locale.CANADA_FRENCH ) ;
String output = ld.format( f );
Dump to console.
System.out.println( "ld: " + ld + " | output: " + output );
ld: 2009-05-19 | output: mardi 19 mai 2009
See in action in IdeOne.com.
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.
You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes.
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
Later versions of Android bundle implementations of the java.time classes.
For earlier Android (<26), the ThreeTenABP project adapts ThreeTen-Backport (mentioned above). 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.

Use the SimpleDateFormat class:
private Date parseDate(String date, String format) throws ParseException
{
SimpleDateFormat formatter = new SimpleDateFormat(format);
return formatter.parse(date);
}
Usage:
Date date = parseDate("19/05/2009", "dd/MM/yyyy");
For efficiency, you would want to store your formatters in a hashmap. The hashmap is a static member of your util class.
private static Map<String, SimpleDateFormat> hashFormatters = new HashMap<String, SimpleDateFormat>();
public static Date parseDate(String date, String format) throws ParseException
{
SimpleDateFormat formatter = hashFormatters.get(format);
if (formatter == null)
{
formatter = new SimpleDateFormat(format);
hashFormatters.put(format, formatter);
}
return formatter.parse(date);
}

Convert a string date to java.sql.Date
String fromDate = "19/05/2009";
DateFormat df = new SimpleDateFormat("dd/MM/yyyy");
java.util.Date dtt = df.parse(fromDate);
java.sql.Date ds = new java.sql.Date(dtt.getTime());
System.out.println(ds);//Mon Jul 05 00:00:00 IST 2010

Check the javadocs for java.text.SimpleDateFormat It describes everything you need.

While SimpleDateFormat will indeed work for your needs, additionally you might want to check out Joda Time, which is apparently the basis for the redone Date library in Java 7. While I haven't used it a lot, I've heard nothing but good things about it and if your manipulating dates extensively in your projects it would probably be worth looking into.

Simple way to format a date and convert into string
Date date= new Date();
String dateStr=String.format("%td/%tm/%tY", date,date,date);
System.out.println("Date with format of dd/mm/dd: "+dateStr);
output:Date with format of dd/mm/dd: 21/10/2015

Suppose that you have a string like this :
String mDate="2019-09-17T10:56:07.827088"
Now we want to change this String format separate date and time in Java and Kotlin.
JAVA:
we have a method for extract date :
public String getDate() {
try {
DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS", Locale.US);
Date date = dateFormat.parse(mDate);
dateFormat = new SimpleDateFormat("MM/dd/yyyy", Locale.US);
return dateFormat.format(date);
} catch (ParseException e) {
e.printStackTrace();
}
return null;
}
Return is this : 09/17/2019
And we have method for extract time :
public String getTime() {
try {
DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS", Locale.US);
Date date = dateFormat.parse(mCreatedAt);
dateFormat = new SimpleDateFormat("h:mm a", Locale.US);
return dateFormat.format(date);
} catch (ParseException e) {
e.printStackTrace();
}
return null;
}
Return is this : 10:56 AM
KOTLIN:
we have a function for extract date :
fun getDate(): String? {
var dateFormat = SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS", Locale.US)
val date = dateFormat.parse(mDate!!)
dateFormat = SimpleDateFormat("MM/dd/yyyy", Locale.US)
return dateFormat.format(date!!)
}
Return is this : 09/17/2019
And we have method for extract time :
fun getTime(): String {
var dateFormat = SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS", Locale.US)
val time = dateFormat.parse(mDate!!)
dateFormat = SimpleDateFormat("h:mm a", Locale.US)
return dateFormat.format(time!!)
}
Return is this : 10:56 AM

A Date object has no format, it is a representation. The date can be presented by a String with the format you like.
E.g. "yyyy-MM-dd", "yy-MMM-dd", "dd-MMM-yy" and etc.
To acheive this you can get the use of the SimpleDateFormat
Try this,
String inputString = "19/05/2009"; // i.e. (dd/MM/yyyy) format
SimpleDateFormat fromUser = new SimpleDateFormat("dd/MM/yyyy");
SimpleDateFormat myFormat = new SimpleDateFormat("yyyy-MM-dd");
try {
Date dateFromUser = fromUser.parse(inputString); // Parse it to the exisitng date pattern and return Date type
String dateMyFormat = myFormat.format(dateFromUser); // format it to the date pattern you prefer
System.out.println(dateMyFormat); // outputs : 2009-05-19
} catch (ParseException e) {
e.printStackTrace();
}
This outputs : 2009-05-19

There are multiple ways to do it, but a very practical one is the use String.format which you can use with java.util.Date or java.util.Calendar or event java.time.LocalDate.
String.format is backed by java.util.Formatter.
I like the omnivore take on it.
class Playground {
public static void main(String[ ] args) {
String formatString = "Created on %1$td/%1$tm/%1$tY%n";
System.out.println(String.format(formatString, new java.util.Date()));
System.out.println(String.format(formatString, java.util.Calendar.getInstance()));
System.out.println(String.format(formatString, java.time.LocalDate.now()));
}
}
The output will be in all cases:
Created on 04/12/2022
Created on 04/12/2022
Created on 04/12/2022