Develop Reference

problems converting date to long

I am pulling data out of an Excel sheet, to load into Hubspot, using Java.
Here is how the data looks:
this date 2018-12-31 becomes Dec 31, 2017 once it's in side Hubspot.
This is wrong!
Here is my code:
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
df.setTimeZone(TimeZone.getTimeZone("UTC"));
Date dt = null;
try {
dt = df.parse(member.getUsageEndDate());
} catch (java.text.ParseException e3) {
//dt = null;
e3.printStackTrace();
}
Long l = dt.getTime();
If I open the data in Notepad, it looks like this: 31-May-2018
How can I get this converted properly?

tl;dr
OffsetDateTime.of(
LocalDate.parse( "2018-12-31" ) ,
LocalTime.MIN ,
ZoneOffset.UTC
)
.toInstant()
.toEpochMilli()
1546214400000
Details
Avoid legacy date-time classes
You are using troublesome old date-time classes long ago made legacy by the arrival of the java.time classes built into Java 8 and later.
ISO 8601
Your input string happens to comply with the ISO 8601 standard formats. These formats are used by default in java.time when parsing/generating strings. So no need to specify a formatting pattern.
LocalDate ld = LocalDate.parse( "2018-12-31" ) ;
First moment of the day
Apparently you need the first moment of the day in UTC for that date. Use OffsetDateTime with constant ZoneOffset.UTC.
OffsetDateTime odt = OffsetDateTime.of( ld , LocalTime.MIN , ZoneOffset.UTC ) ;
Dump to console.
System.out.println( "odt.toString(): " + odt );
See this code run live at IdeOne.com.
odt.toString(): 2018-12-31T00:00Z
Count-from-epoch
You appear to want the count of milliseconds since the epoch reference date of first moment of 1970 in UTC, 1970-01-01T00:00Z. Extract an Instant object, the basic building-block class in java.time, and call its handy Instant::toEpochMilli method.
long millisecondsSinceEpoch = odt.toInstant().toEpochMilli() ;
See this code run live at IdeOne.com.
1546214400000
Going the other direction.
Instant instant = Instant.ofEpochMilli( 1_546_214_400_000L ) ;
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.

Unexpected exception while parsing date

I am trying to parse the date according to the following code but getting exception. Below is the code -
public class DateTest {
public static void main(String args []) {
String start = "23-Jan-2017";
DateFormat dateFormatTripStartDate = new SimpleDateFormat("dd-MMM-yyyy hh:mm a");
try {
Date parsedDate = dateFormatTripStartDate.parse(start);
System.out.println(parsedDate);
} catch (ParseException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
Exception :
java.text.ParseException: Unparseable date: "23-Jan-2017"
at java.text.DateFormat.parse(DateFormat.java:357)
at DateTest.main(DateTest.java:18)
Kindly help me identify the problem. Thanks.

Remove the time part in your pattern:
DateFormat dateFormatTripStartDate = new SimpleDateFormat("dd-MMM-yyyy");

tl;dr
LocalDate.parse(
"23-Jan-2017" ,
DateTimeFormatter.ofPattern( "dd-MMM-uuuu" , Locale.US )
)
Using java.time
Other Answers are correct about formatting pattern mismatching input data. But both the Question and other Answers are outdated.
The modern way is with java.time classes that supplant the troublesome old date-time classes.
The LocalDate class represents a date-only value without time-of-day and without time zone.
DateTimeFormatter f = DateTimeFormatter.ofPattern( "dd-MMM-uuuu" , Locale.US );
LocalDate ld = LocalDate.parse( "23-Jan-2017" , f );
ld.toString(): 2017-01-23
Specify the Locale as that determines the human language used to translate the name of the month. If omitted the JVM’s current default Locale is used implicitly. That default can be changed at any moment by any code in any thread of any app within the JVM, so do not rely upon it.
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 and 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 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, andfz more.

First of all, the answer from kamehl23 is correct. Your parsed string may not be missing any parst that are specified in format and thus you will need to modify your format to DateFormat dateFormatTripStartDate = new SimpleDateFormat("dd-MMM-yyyy"); However just to add few more interesting options: Remember that SimpleDateFormat is not thread safe and in general not recommended. Sensible pre Java 8 options are Apache FastDateFormat and joda-time package. Both have some problems but certainly by far better then SimpleDateFormat (Joda-time package is very popular). In Java 8 a new date and time hanling was introduced with package java.time.format It takes time to adjust to it but it works wonderful and resolves many problems that existed in that area. See class DateTimeFormatter.And finally, I once had to write a utility that can take a String in any format and attempt to parse it to Date if possible. I wrote an article that describes how I implemented that Utility. I wrote it in Java 8, but the idea could be implemented in any version. See Java 8 java.time package: parsing any string to date

You are using pattern "dd-MMM-yyyy hh:mm a". But in actual "hh:mm a" part is not present in the "23-Jan-2017" value. Because of this parse function is not able to parse the String date.
So change your pattern to "dd-MMM-yyyy" which matches your date string. This will remove the exception you are getting.

Convert date or calendar type into string format

So, basically I am trying to achieve the following format in a String:
2012-06-17T08:00:00.000+01:00
I get the original date in a string format which I then parse into different formats.
When I use SimpleDateFormat with the format as (yyyy-MM-dd'T'HH:mm:ss.sssZ), I get the following output:
2013-06-17T07:00:00.000+0530
Here +0530 should be +05:30
When I set the above date into a Calendar type and then convert it to a string I get the following format:
2013-06-17T07:00:00+05:30
Here I don't get the .000 after the seconds.
Any ideas how this can be achieved, without using JodaTime. Need manipulations in Date, String and Calendar type only

Firstly to get the extra : use XXX in your formatter like so and use Uppercase S to get the milliseconds
SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSXXX")
UPDATE: Above doesn't work on 1.6
Yo could try the following however
SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSZ")
{
public StringBuffer format(Date date, StringBuffer toAppendTo, java.text.FieldPosition pos)
{
StringBuffer toFix = super.format(date, toAppendTo, pos);
return toFix.insert(toFix.length()-2, ':');
};
See this post for more

SimpleDateFormat pattern
"yyyy-MM-dd'T'HH:mm:ss.SSSXXX"

tl;dr
OffsetDateTime.parse( "2012-06-17T08:00:00.000+01:00" ) // Parse string in standard ISO 8601 format to an object.
.format( // Generate a String representing the value of that `OffsetDateTime` object.
DateTimeFormatter.ofPattern( "uuuu-MM-dd'T'HH:mm:ss.SSSXXXXX" ) // Specify a formatting pattern to force the seconds and fractional second even if zero.
) // Return a `String` object.
2012-06-17T08:00:00.000+01:00
java.time
The modern approach uses the java.time classes rather than the troublesome old legacy date-time classes. Avoid Date, Calendar, and SimpleDateFormat.
ISO 8601
Your desired format happens to be standard ISO 8601 format. The java.time classes use the standard format by default when parsing/generating strings. So no need to specify a formatting pattern.
OffsetDateTime
Your input string includes an offset-from-offset but not a time zone. So we parse as a OffsetDateTime object.
OffsetDateTime odt = OffsetDateTime.parse( "2012-06-17T08:00:00.000+01:00" ) ;
To generate a string in the same standard ISO 8601 format, simply call toString. By default, the least significant parts are omitted if zero. So no seconds or fractional second appear using your example data.
String output = odt.toString() ;
2012-06-17T08:00+01:00
If you want to force the seconds and fractional second even when zero, specify a formatting pattern.
OffsetDateTime odt = OffsetDateTime.parse( "2012-06-17T08:00:00.000+01:00" );
DateTimeFormatter f = DateTimeFormatter.ofPattern( "uuuu-MM-dd'T'HH:mm:ss.SSSXXXXX" );
String output = odt.format( f );
2012-06-17T08:00:00.000+01:00
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.

Formatting Date in Thread safe Manner throws java.text.ParseException:

I am trying to convert the date from one format to Another
Input String - 2012-11-07-121603 (yyyy-MM-dd-HH-mm-ss)
Output String - 2012-11-07-12:16:03:000 (yyyy-MM-dd-HH:mm:ss:SSS)
ThreadSafeSimpleDateFormatUtil simpleDateFormat = new ThreadSafeSimpleDateFormatUtil(GenericConstants.DATE_FORMAT.YYYY_MM_DD_HH_MM_SS.toString());
final Date parsedDate = simpleDateFormat.parse(bulkCollectionTime);
simpleDateFormat = new ThreadSafeSimpleDateFormatUtil(GenericConstants.DATE_FORMAT.YYYY_MM_DD_HH_MM_SS_SSS.toString());
writeBean.setTimestamp(simpleDateFormat.format(parsedDate));
But it's throwing below error:
java.text.ParseException: Unparseable date: "2012-11-07-121603"
at java.text.DateFormat.parse(DateFormat.java:337)
at com.belgacom.rosy.rebecca.utils.ThreadSafeSimpleDateFormatUtil.parse(ThreadSafeSimpleDateFormatUtil.java:39)

Looks like the input format should be without the "-" between hours, minutes and seconds:
2012-11-07-121603 (yyyy-MM-dd-HHmmss)

Input String - 2012-11-07-121603 (yyyy-MM-dd-HH-mm-ss)
wrong pattern it would match with yyyy-MM-dd-HHmmss.

tl;dr
LocalDateTime.parse(
"2012-11-07-121603" ,
DateTimeFormatter.ofPattern( "uuu-MM-dd-HHmmss" )
).toString()
2012-11-07T12:16:03
java.time
The modern approach uses the java.time classes built into Java 8 and later. These classes are inherently thread-safe. These classes supplant the troublesome old legacy date-time classes that are un-thread-safe.
String input = "2012-11-07-121603" ;
DateTimeFormatter f = DateTimeFormatter.ofPattern( "uuu-MM-dd-HHmmss" ) ;
Parse as a LocalDateTime because your input lacks info about time zone or offset-from-UTC.
LocalDateTime ldt = LocalDateTime.parse( input , f );
ldt.toString(): 2012-11-07T12:16:03
Thread-safety
The java.time classes are designed to be thread-safe. The classes use immutable objects. You may cache objects such as DateTimeFormatter for re-use throughout your code and across threads.
ISO 8601
When serializing date-time values to text, use standard ISO 8601 formats only. Do not invent your own formats such as that shown in your Question. The standard formats are practical and sensible. They are designed to be easy to parse by machine yet easy to read by humans across cultures.
The java.time classes use ISO 8601 formats by default when parsing/generating strings. Example shown above.
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.

how to convert timestamp string to java.util.Date

I need to convert a timestamp string to java.util.Date. E.g.:
MMDDYYHHMMSS to MM-DD-YY HH-MM-SS
Where MM is month, DD is date, YY is year, HH is hours, MM is minutes and SS is seconds.

You can do it like this:
DateFormat format = new SimpleDateFormat("MMddyyHHmmss");
Date date = format.parse("022310141505");
but I would strongly recommend that you use Joda Time instead. It's a better date/time library by a long, long way. In particular, the formatters/parsers in Joda Time are thread-safe, so you can reuse them freely and statically; java.text.SimpleDateFormat isn't thread-safe, so you either need to create one per thread or serialize access to it with a synchronized block.

tl;dr
java.time.LocalDateTime.parse(
"012318123456" ,
DateTimeFormatter.ofPattern( "MMdduuHHmmss" )
).format(
DateTimeFormatter.ofPattern( "MM-dd-uu HH-mm-ss" )
)
01-23-18 12-34-56
java.time
The modern approach uses the java.time classes.
Define a formatting pattern to match your input string.
DateTimeFormatter f = DateTimeFormatter.ofPattern( "MMdduuHHmmss" ) ;
Your two-digit year will be interpreted as being 21st century ( 20xx ).
Parse as a LocalDateTime because your input string lacks any indicator of time zone or offset-from-UTC.
LocalDateTime ldt = LocalDateTime.parse( "012318123456" , f ) ;
ldt.toString(): 2018-01-23T12:34:56
Generate a string in your desired format.
DateTimeFormatter fOut = DateTimeFormatter.ofPattern( "MM-dd-uu HH-mm-ss" ) ;
String output = ldt.format( fOut );
01-23-18 12-34-56
ISO 8601
Both of your formats are terrible, for multiple reasons.
When serializing date-time values, use the standard ISO 8601 formats whenever possible. They are designed to be practical, easy to parse by machine, easy to read by humans across cultures.
For a date-time time such as yours, the T in the middle separates the date portion from the time-of-day portion.
2018-01-23T12:34:56
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
Later versions of Android bundle implementations of the java.time classes.
For earlier Android, 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 a SimpleDateFormat with an appropriate format string (be careful to use the correct format letters, uppercase and lowercase have different meanings!).