Java string to date conversion

That’s the hard way, and those java.util.Date setter methods have been deprecated since Java 1.1 (1997). Moreover, the whole java.util.Date class was de-facto deprecated (discommended) since introduction of java.time API in Java 8 (2014).

Simply format the date using DateTimeFormatter with a pattern matching the input string (the tutorial is available here).

In your specific case of “January 2, 2010” as the input string:

  1. “January” is the full text month, so use the MMMM pattern for it
  2. “2” is the short day-of-month, so use the d pattern for it.
  3. “2010” is the 4-digit year, so use the yyyy pattern for it.
String string = "January 2, 2010";
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("MMMM d, yyyy", Locale.ENGLISH);
LocalDate date = LocalDate.parse(string, formatter);
System.out.println(date); // 2010-01-02

Note: if your format pattern happens to contain the time part as well, then use LocalDateTime#parse(text, formatter) instead of LocalDate#parse(text, formatter). And, if your format pattern happens to contain the time zone as well, then use ZonedDateTime#parse(text, formatter) instead.

Here’s an extract of relevance from the javadoc, listing all available format patterns:

GeratextAD; Anno Domini; A
uyearyear2004; 04
yyear-of-erayear2004; 04
M/Lmonth-of-yearnumber/text7; 07; Jul; July; J
Q/qquarter-of-yearnumber/text3; 03; Q3; 3rd quarter
Yweek-based-yearyear1996; 96
Eday-of-weektextTue; Tuesday; T
e/clocalized day-of-weeknumber/text2; 02; Tue; Tuesday; T
hclock-hour-of-am-pm (1-12)number12
Khour-of-am-pm (0-11)number0
kclock-hour-of-am-pm (1-24)number0
Hhour-of-day (0-23)number0
Vtime-zone IDzone-idAmerica/Los_Angeles; Z; -08:30
ztime-zone namezone-namePacific Standard Time; PST
Olocalized zone-offsetoffset-OGMT+8; GMT+08:00; UTC-08:00;
Xzone-offset ‘Z’ for zerooffset-XZ; -08; -0830; -08:30; -083015; -08:30:15;
xzone-offsetoffset-x+0000; -08; -0830; -08:30; -083015; -08:30:15;
Zzone-offsetoffset-Z+0000; -0800; -08:00;

Do note that it has several predefined formatters for the more popular patterns. So instead of e.g. DateTimeFormatter.ofPattern("EEE, d MMM yyyy HH:mm:ss Z", Locale.ENGLISH);, you could use DateTimeFormatter.RFC_1123_DATE_TIME. This is possible because they are, on the contrary to SimpleDateFormat, thread safe. You could thus also define your own, if necessary.

For a particular input string format, you don’t need to use an explicit DateTimeFormatter: a standard ISO 8601 date, like 2016-09-26T17:44:57Z, can be parsed directly with LocalDateTime#parse(text) as it already uses the ISO_LOCAL_DATE_TIME formatter. Similarly, LocalDate#parse(text) parses an ISO date without the time component (see ISO_LOCAL_DATE), and ZonedDateTime#parse(text) parses an ISO date with an offset and time zone added (see ISO_ZONED_DATE_TIME).

Pre-Java 8

In case you’re not on Java 8 yet, or are forced to use java.util.Date, then format the date using SimpleDateFormat using a format pattern matching the input string.

String string = "January 2, 2010";
DateFormat format = new SimpleDateFormat("MMMM d, yyyy", Locale.ENGLISH);
Date date = format.parse(string);
System.out.println(date); // Sat Jan 02 00:00:00 GMT 2010

Note the importance of the explicit Locale argument. If you omit it, then it will use the default locale which is not necessarily English as used in the month name of the input string. If the locale doesn’t match with the input string, then you would confusingly get a java.text.ParseException even though when the format pattern seems valid.

Here’s an extract of relevance from the javadoc, listing all available format patterns:

LetterDate or Time ComponentPresentationExamples
GEra designatorTextAD
yYearYear1996; 96
YWeek yearYear2009; 09
M/LMonth in yearMonthJuly; Jul; 07
wWeek in yearNumber27
WWeek in monthNumber2
DDay in yearNumber189
dDay in monthNumber10
FDay of week in monthNumber2
EDay in weekTextTuesday; Tue
uDay number of weekNumber1
aAm/pm markerTextPM
HHour in day (0-23)Number0
kHour in day (1-24)Number24
KHour in am/pm (0-11)Number0
hHour in am/pm (1-12)Number12
mMinute in hourNumber30
sSecond in minuteNumber55
zTime zoneGeneral time zonePacific Standard Time; PST; GMT-08:00
ZTime zoneRFC 822 time zone-0800
XTime zoneISO 8601 time zone-08; -0800; -08:00

Note that the patterns are case sensitive and that text based patterns of four characters or more represent the full form; otherwise a short or abbreviated form is used if available. So e.g. MMMMM or more is unnecessary.

Here are some examples of valid SimpleDateFormat patterns to parse a given string to date:

Input stringPattern
2001.07.04 AD at 12:08:56 PDTyyyy.MM.dd G 'at' HH:mm:ss z
Wed, Jul 4, ’01EEE, MMM d, ''yy
12:08 PMh:mm a
12 o’clock PM, Pacific Daylight Timehh 'o''clock' a, zzzz
0:08 PM, PDTK:mm a, z
02001.July.04 AD 12:08 PMyyyyy.MMMM.dd GGG hh:mm aaa
Wed, 4 Jul 2001 12:08:56 -0700EEE, d MMM yyyy HH:mm:ss Z

An important note is that SimpleDateFormat is not thread safe. In other words, you should never declare and assign it as a static or instance variable and then reuse it from different methods/threads. You should always create it brand new within the method local scope.

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