java.text

Class SimpleDateFormat

java.lang.Object

java.text.DateFormat

java.text.SimpleDateFormat

public class SimpleDateFormat
extends DateFormat

SimpleDateFormat is a concrete class for formatting and parsing dates in a locale-sensitive manner. It allows for formatting (date → text), parsing (text → date), and normalization.

SimpleDateFormat allows you to start by choosing any user-defined patterns for date-time formatting. However, you are encouraged to create a date-time formatter with either getTimeInstance, getDateInstance, or getDateTimeInstance in DateFormat. Each of these class methods can return a date/time formatter initialized with a default format pattern. You may modify the format pattern using the applyPattern methods as desired. For more information on using these methods, see DateFormat.

Date and Time Patterns

Date and time formats are specified by date and time pattern strings. Within date and time pattern strings, unquoted letters from 'A' to 'Z' and from 'a' to 'z' are interpreted as pattern letters representing the components of a date or time string. Text can be quoted using single quotes (') to avoid interpretation. "''" represents a single quote. All other characters are not interpreted; they're simply copied into the output string during formatting or matched against the input string during parsing.

The following pattern letters are defined (all other characters from 'A' to 'Z' and from 'a' to 'z' are reserved):

Letter	Date or Time Component	Presentation	Examples
G	Era designator	Text	AD
y	Year	Year	1996; 96
Y	Week year	Year	2009; 09
M	Month in year	Month	July; Jul; 07
w	Week in year	Number	27
W	Week in month	Number	2
D	Day in year	Number	189
d	Day in month	Number	10
F	Day of week in month	Number	2
E	Day name in week	Text	Tuesday; Tue
u	Day number of week (1 = Monday, ..., 7 = Sunday)	Number	1
a	Am/pm marker	Text	PM
H	Hour in day (0-23)	Number	0
k	Hour in day (1-24)	Number	24
K	Hour in am/pm (0-11)	Number	0
h	Hour in am/pm (1-12)	Number	12
m	Minute in hour	Number	30
s	Second in minute	Number	55
S	Millisecond	Number	978

Pattern letters are usually repeated, as their number determines the exact presentation:

• Text: For formatting, if the number of pattern letters is 4 or more, the full form is used; otherwise a short or abbreviated form is used if available. For parsing, both forms are accepted, independent of the number of pattern letters.
  
  
• Number: For formatting, the number of pattern letters is the minimum number of digits, and shorter numbers are zero-padded to this amount. For parsing, the number of pattern letters is ignored unless it's needed to separate two adjacent fields.
  
  
• Year: If the formatter's Calendar is the Gregorian calendar, the following rules are applied.
  
  • For formatting, if the number of pattern letters is 2, the year is truncated to 2 digits; otherwise it is interpreted as a number.
  • For parsing, if the number of pattern letters is more than 2, the year is interpreted literally, regardless of the number of digits. So using the pattern "MM/dd/yyyy", "01/11/12" parses to Jan 11, 12 A.D.
  • For parsing with the abbreviated year pattern ("y" or "yy"), SimpleDateFormat must interpret the abbreviated year relative to some century. It does this by adjusting dates to be within 80 years before and 20 years after the time the SimpleDateFormat instance is created. For example, using a pattern of "MM/dd/yy" and a SimpleDateFormat instance created on Jan 1, 1997, the string "01/11/12" would be interpreted as Jan 11, 2012 while the string "05/04/64" would be interpreted as May 4, 1964. During parsing, only strings consisting of exactly two digits, as defined by Character.isDigit(char), will be parsed into the default century. Any other numeric string, such as a one digit string, a three or more digit string, or a two digit string that isn't all digits (for example, "-1"), is interpreted literally. So "01/02/3" or "01/02/003" are parsed, using the same pattern, as Jan 2, 3 AD. Likewise, "01/02/-3" is parsed as Jan 2, 4 BC.
  Otherwise system specific forms are applied. For both formatting and parsing, if the number of pattern letters is 4 or more, a calendar specific long form is used. Otherwise, a calendar specific short or abbreviated form is used.
  
  
• Month: If the number of pattern letters is 3 or more, the month is interpreted as text; otherwise, it is interpreted as a number.
  
  

Examples

The following examples show how date and time patterns are interpreted.

Date and Time Pattern	Result
"yyyy.MM.dd G 'at' HH:mm:ss z"	2001.07.04 AD at 12:08:56 PDT
"EEE, MMM d, ''yy"	Wed, Jul 4, '01
"h:mm a"	12:08 PM
"hh 'o''clock' a, zzzz"	12 o'clock PM, Pacific Daylight Time
"K:mm a, z"	0:08 PM, PDT
"yyyyy.MMMMM.dd GGG hh:mm aaa"	02001.July.04 AD 12:08 PM
"EEE, d MMM yyyy HH:mm:ss Z"	Wed, 4 Jul 2001 12:08:56 -0700
"yyMMddHHmmssZ"	010704120856-0700
"yyyy-MM-dd'T'HH:mm:ss.SSSZ"	2001-07-04T12:08:56.235-0700
"yyyy-MM-dd'T'HH:mm:ss.SSSXXX"	2001-07-04T12:08:56.235-07:00
"YYYY-'W'ww-u"	2001-W27-3

Synchronization

Date formats are not synchronized. It is recommended to create separate format instances for each thread. If multiple threads access a format concurrently, it must be synchronized externally.

Author:

Mark Davis, Chen-Lieh Huang, Alan Liu

See Also:

Java Tutorial, Calendar, DateFormat, DateFormatSymbols

Field Summary

Fields inherited from class java.text.DateFormat

calendar, DEFAULT, FULL, LONG, MEDIUM, SHORT

Constructor Summary

Constructors

Constructor and Description
SimpleDateFormat() Constructs a SimpleDateFormat using the default pattern and date format symbols.
SimpleDateFormat(String pattern) Constructs a SimpleDateFormat using the given pattern and the default date format symbols.
SimpleDateFormat(String pattern, DateFormatSymbols formatSymbols) Constructs a SimpleDateFormat using the given pattern and date format symbols.

Method Summary

Modifier and Type	Method and Description
void	applyPattern(String pattern) Applies the given pattern string to this date format.
String	format(Date date) Formats a Date into a date/time string.
DateFormatSymbols	getDateFormatSymbols() Gets a copy of the date and time format symbols of this date format.
void	setDateFormatSymbols(DateFormatSymbols newFormatSymbols) Sets the date and time format symbols of this date format.
String	toPattern() Returns a pattern string describing this date format.

Methods inherited from class java.text.DateFormat

getCalendar, getDateInstance, getDateInstance, getDateTimeInstance, getDateTimeInstance, getInstance, getTimeInstance, getTimeInstance, setCalendar

Methods inherited from class java.lang.Object

clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

SimpleDateFormat

public SimpleDateFormat()

Constructs a SimpleDateFormat using the default pattern and date format symbols. Note: This constructor may not support all locales. For full coverage, use the factory methods in the DateFormat class.

SimpleDateFormat

public SimpleDateFormat(String pattern)

Constructs a SimpleDateFormat using the given pattern and the default date format symbols. For full coverage, use the factory methods in the DateFormat class.

This is equivalent to calling.

Parameters:

pattern - the pattern describing the date and time format

Throws:

NullPointerException - if the given pattern is null

IllegalArgumentException - if the given pattern is invalid

SimpleDateFormat

public SimpleDateFormat(String pattern,
                        DateFormatSymbols formatSymbols)

Constructs a SimpleDateFormat using the given pattern and date format symbols.

Parameters:

pattern - the pattern describing the date and time format

formatSymbols - the date format symbols to be used for formatting

Throws:

NullPointerException - if the given pattern or formatSymbols is null

IllegalArgumentException - if the given pattern is invalid

Method Detail

applyPattern

public void applyPattern(String pattern)

Applies the given pattern string to this date format.

Parameters:

pattern - the new date and time pattern for this date format

Throws:

NullPointerException - if the given pattern is null

IllegalArgumentException - if the given pattern is invalid

format

public String format(Date date)

Description copied from class: DateFormat

Formats a Date into a date/time string.

Specified by:

format in class DateFormat

Parameters:

date - the time value to be formatted into a time string.

Returns:

the formatted time string.

getDateFormatSymbols

public DateFormatSymbols getDateFormatSymbols()

Gets a copy of the date and time format symbols of this date format.

Returns:

the date and time format symbols of this date format

See Also:

setDateFormatSymbols(java.text.DateFormatSymbols)

setDateFormatSymbols

public void setDateFormatSymbols(DateFormatSymbols newFormatSymbols)

Sets the date and time format symbols of this date format.

Parameters:

newFormatSymbols - the new date and time format symbols

Throws:

NullPointerException - if the given newFormatSymbols is null

See Also:

getDateFormatSymbols()

toPattern

public String toPattern()

Returns a pattern string describing this date format.

Returns:

a pattern string describing this date format.