com.ibm.icu.text

Class 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 {@link DateFormat}.

Time Format Syntax:

To specify the time format use a time pattern string. In this pattern, all ASCII letters are reserved as pattern letters, which are defined as the following:

 Symbol   Meaning                 Presentation        Example
 ------   -------                 ------------        -------
 G        era designator          (Text)              AD
 y†       year                    (Number)            1996
 Y*       year (week of year)     (Number)            1997
 u*       extended year           (Number)            4601
 M        month in year           (Text & Number)     July & 07
 d        day in month            (Number)            10
 h        hour in am/pm (1~12)    (Number)            12
 H        hour in day (0~23)      (Number)            0
 m        minute in hour          (Number)            30
 s        second in minute        (Number)            55
 S        fractional second       (Number)            978
 E        day of week             (Text)              Tuesday
 e*       day of week (local 1~7) (Number)            2
 D        day in year             (Number)            189
 F        day of week in month    (Number)            2 (2nd Wed in July)
 w        week in year            (Number)            27
 W        week in month           (Number)            2
 a        am/pm marker            (Text)              PM
 k        hour in day (1~24)      (Number)            24
 K        hour in am/pm (0~11)    (Number)            0
 z        time zone               (Text)              Pacific Standard Time
 Z        time zone (RFC 822)     (Number)            -0800
 v        time zone (generic)     (Text)              Pacific Time
 g*       Julian day              (Number)            2451334
 A*       milliseconds in day     (Number)            69540000
 '        escape for text         (Delimiter)         'Date='
 ''       single quote            (Literal)           'o''clock'
 
* These items are not supported by Java's SimpleDateFormat.
ICU interprets a single 'y' differently than Java.

The count of pattern letters determine the format.

(Text): 4 or more pattern letters--use full form, < 4--use short or abbreviated form if one exists.

(Number): the minimum number of digits. Shorter numbers are zero-padded to this amount. Year is handled specially; that is, if the count of 'y' is 2, the Year will be truncated to 2 digits. (e.g., if "yyyy" produces "1997", "yy" produces "97".) Unlike other fields, fractional seconds are padded on the right with zero.

(Text & Number): 3 or over, use text, otherwise use number.

Any characters in the pattern that are not in the ranges of ['a'..'z'] and ['A'..'Z'] will be treated as quoted text. For instance, characters like ':', '.', ' ', '#' and '@' will appear in the resulting time text even they are not embraced within single quotes.

A pattern containing any invalid pattern letter will result in a thrown exception during formatting or parsing.

Examples Using the US Locale:

 Format Pattern                         Result
 --------------                         -------
 "yyyy.MM.dd G 'at' HH:mm:ss vvvv" ->>  1996.07.10 AD at 15:08:56 Pacific Time
 "EEE, MMM d, ''yy"                ->>  Wed, July 10, '96
 "h:mm a"                          ->>  12:08 PM
 "hh 'o''clock' a, zzzz"           ->>  12 o'clock PM, Pacific Daylight Time
 "K:mm a, vvv"                     ->>  0:00 PM, PT
 "yyyyy.MMMMM.dd GGG hh:mm aaa"    ->>  01996.July.10 AD 12:08 PM
 
Code Sample:
 SimpleTimeZone pdt = new SimpleTimeZone(-8 * 60 * 60 * 1000, "PST");
 pdt.setStartRule(Calendar.APRIL, 1, Calendar.SUNDAY, 2*60*60*1000);
 pdt.setEndRule(Calendar.OCTOBER, -1, Calendar.SUNDAY, 2*60*60*1000);
 
// Format the current time. SimpleDateFormat formatter = new SimpleDateFormat ("yyyy.MM.dd G 'at' hh:mm:ss a zzz"); Date currentTime_1 = new Date(); String dateString = formatter.format(currentTime_1);
// Parse the previous string back into a Date. ParsePosition pos = new ParsePosition(0); Date currentTime_2 = formatter.parse(dateString, pos);
In the example, the time value currentTime_2 obtained from parsing will be equal to currentTime_1. However, they may not be equal if the am/pm marker 'a' is left out from the format pattern while the "hour in am/pm" pattern symbol is used. This information loss can happen when formatting the time in PM.

When parsing a date string using the abbreviated year pattern ("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 {@link java.lang.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.

If the year pattern does not have exactly two 'y' characters, 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.

When numeric fields abut one another directly, with no intervening delimiter characters, they constitute a run of abutting numeric fields. Such runs are parsed specially. For example, the format "HHmmss" parses the input text "123456" to 12:34:56, parses the input text "12345" to 1:23:45, and fails to parse "1234". In other words, the leftmost field of the run is flexible, while the others keep a fixed width. If the parse fails anywhere in the run, then the leftmost field is shortened by one character, and the entire run is parsed again. This is repeated until either the parse succeeds or the leftmost field is one character in length. If the parse still fails at that point, the parse of the run fails.

For time zones that have no names, use strings GMT+hours:minutes or GMT-hours:minutes.

The calendar defines what is the first day of the week, the first week of the year, whether hours are zero based or not (0 vs 12 or 24), and the time zone. There is one common decimal format to handle all the numbers; the digit count is handled programmatically according to the pattern.

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: Calendar GregorianCalendar TimeZone DateFormat DateFormatSymbols DecimalFormat

UNKNOWN: ICU 2.0

Constructor Summary
SimpleDateFormat()
Construct a SimpleDateFormat using the default pattern for the default locale.
SimpleDateFormat(String pattern)
Construct a SimpleDateFormat using the given pattern in the default locale.
SimpleDateFormat(String pattern, Locale loc)
Construct a SimpleDateFormat using the given pattern and locale.
SimpleDateFormat(String pattern, ULocale loc)
Construct a SimpleDateFormat using the given pattern and locale.
SimpleDateFormat(String pattern, DateFormatSymbols formatData)
Construct a SimpleDateFormat using the given pattern and locale-specific symbol data.
SimpleDateFormat(String pattern, DateFormatSymbols formatData, ULocale loc)
Method Summary
voidapplyLocalizedPattern(String pattern)
Apply the given localized pattern string to this date format.
voidapplyPattern(String pattern)
Apply the given unlocalized pattern string to this date format.
Objectclone()
Overrides Cloneable
booleanequals(Object obj)
Override equals.
StringBufferformat(Calendar cal, StringBuffer toAppendTo, FieldPosition pos)
Overrides DateFormat.
Dateget2DigitYearStart()
Returns the beginning date of the 100-year period 2-digit years are interpreted as being within.
DateFormatSymbolsgetDateFormatSymbols()
Gets the date/time formatting data.
protected DateFormatSymbolsgetSymbols()
Method for subclasses to access the DateFormatSymbols.
inthashCode()
Override hashCode.
protected intmatchString(String text, int start, int field, String[] data, Calendar cal)
Attempt to match the text at a given position against an array of strings.
voidparse(String text, Calendar cal, ParsePosition parsePos)
Overrides DateFormat
voidset2DigitYearStart(Date startDate)
Sets the 100-year period 2-digit years will be interpreted as being in to begin on the date the user specifies.
voidsetDateFormatSymbols(DateFormatSymbols newFormatSymbols)
Allows you to set the date/time formatting data.
voidsetNumberFormat(NumberFormat newNumberFormat)
Allows you to set the number formatter.
protected StringsubFormat(char ch, int count, int beginOffset, FieldPosition pos, DateFormatSymbols formatData, Calendar cal)
Format a single field, given its pattern character.
protected voidsubFormat(StringBuffer buf, char ch, int count, int beginOffset, FieldPosition pos, Calendar cal)
Format a single field; useFastFormat variant.
protected intsubParse(String text, int start, char ch, int count, boolean obeyCount, boolean allowNegative, boolean[] ambiguousYear, Calendar cal)
Protected method that converts one field of the input string into a numeric field value in cal.
StringtoLocalizedPattern()
Return a localized pattern string describing this date format.
StringtoPattern()
Return a pattern string describing this date format.
protected voidzeroPaddingNumber(StringBuffer buf, int value, int minDigits, int maxDigits)
Internal high-speed method.
protected StringzeroPaddingNumber(long value, int minDigits, int maxDigits)
Formats a number with the specified minimum and maximum number of digits.

Constructor Detail

SimpleDateFormat

public SimpleDateFormat()
Construct a SimpleDateFormat using the default pattern for the default locale. Note: Not all locales support SimpleDateFormat; for full generality, use the factory methods in the DateFormat class.

See Also: DateFormat

UNKNOWN: ICU 2.0

SimpleDateFormat

public SimpleDateFormat(String pattern)
Construct a SimpleDateFormat using the given pattern in the default locale. Note: Not all locales support SimpleDateFormat; for full generality, use the factory methods in the DateFormat class.

UNKNOWN: ICU 2.0

SimpleDateFormat

public SimpleDateFormat(String pattern, Locale loc)
Construct a SimpleDateFormat using the given pattern and locale. Note: Not all locales support SimpleDateFormat; for full generality, use the factory methods in the DateFormat class.

UNKNOWN: ICU 2.0

SimpleDateFormat

public SimpleDateFormat(String pattern, ULocale loc)
Construct a SimpleDateFormat using the given pattern and locale. Note: Not all locales support SimpleDateFormat; for full generality, use the factory methods in the DateFormat class.

UNKNOWN: ICU 3.2 This API might change or be removed in a future release.

SimpleDateFormat

public SimpleDateFormat(String pattern, DateFormatSymbols formatData)
Construct a SimpleDateFormat using the given pattern and locale-specific symbol data. Warning: uses default locale for digits!

UNKNOWN: ICU 2.0

SimpleDateFormat

public SimpleDateFormat(String pattern, DateFormatSymbols formatData, ULocale loc)

UNKNOWN: ICU 3.2

Method Detail

applyLocalizedPattern

public void applyLocalizedPattern(String pattern)
Apply the given localized pattern string to this date format.

UNKNOWN: ICU 2.0

applyPattern

public void applyPattern(String pattern)
Apply the given unlocalized pattern string to this date format.

UNKNOWN: ICU 2.0

clone

public Object clone()
Overrides Cloneable

UNKNOWN: ICU 2.0

equals

public boolean equals(Object obj)
Override equals.

UNKNOWN: ICU 2.0

format

public StringBuffer format(Calendar cal, StringBuffer toAppendTo, FieldPosition pos)
Overrides DateFormat.

Formats a date or time, which is the standard millis since January 1, 1970, 00:00:00 GMT.

Example: using the US locale: "yyyy.MM.dd G 'at' HH:mm:ss zzz" ->> 1996.07.10 AD at 15:08:56 PDT

Parameters: cal the calendar whose date-time value is to be formatted into a date-time string toAppendTo where the new date-time text is to be appended pos the formatting position. On input: an alignment field, if desired. On output: the offsets of the alignment field.

Returns: the formatted date-time string.

See Also: DateFormat

UNKNOWN: ICU 2.0

get2DigitYearStart

public Date get2DigitYearStart()
Returns the beginning date of the 100-year period 2-digit years are interpreted as being within.

Returns: the start of the 100-year period into which two digit years are parsed

UNKNOWN: ICU 2.0

getDateFormatSymbols

public DateFormatSymbols getDateFormatSymbols()
Gets the date/time formatting data.

Returns: a copy of the date-time formatting data associated with this date-time formatter.

UNKNOWN: ICU 2.0

getSymbols

protected DateFormatSymbols getSymbols()
Method for subclasses to access the DateFormatSymbols.

UNKNOWN: ICU 2.0

hashCode

public int hashCode()
Override hashCode. Generates the hash code for the SimpleDateFormat object

UNKNOWN: ICU 2.0

matchString

protected int matchString(String text, int start, int field, String[] data, Calendar cal)
Attempt to match the text at a given position against an array of strings. Since multiple strings in the array may match (for example, if the array contains "a", "ab", and "abc", all will match the input string "abcd") the longest match is returned. As a side effect, the given field of cal is set to the index of the best match, if there is one.

Parameters: text the time text being parsed. start where to start parsing. field the date field being parsed. data the string array to parsed.

Returns: the new start position if matching succeeded; a negative number indicating matching failure, otherwise. As a side effect, sets the cal field field to the index of the best match, if matching succeeded.

UNKNOWN: ICU 2.0

parse

public void parse(String text, Calendar cal, ParsePosition parsePos)
Overrides DateFormat

See Also: DateFormat

UNKNOWN: ICU 2.0

set2DigitYearStart

public void set2DigitYearStart(Date startDate)
Sets the 100-year period 2-digit years will be interpreted as being in to begin on the date the user specifies.

Parameters: startDate During parsing, two digit years will be placed in the range startDate to startDate + 100 years.

UNKNOWN: ICU 2.0

setDateFormatSymbols

public void setDateFormatSymbols(DateFormatSymbols newFormatSymbols)
Allows you to set the date/time formatting data.

Parameters: newFormatSymbols the new symbols

UNKNOWN: ICU 2.0

setNumberFormat

public void setNumberFormat(NumberFormat newNumberFormat)
Allows you to set the number formatter.

Parameters: newNumberFormat the given new NumberFormat.

UNKNOWN: ICU 2.0

subFormat

protected String subFormat(char ch, int count, int beginOffset, FieldPosition pos, DateFormatSymbols formatData, Calendar cal)
Format a single field, given its pattern character. Subclasses may override this method in order to modify or add formatting capabilities.

Parameters: ch the pattern character count the number of times ch is repeated in the pattern beginOffset the offset of the output string at the start of this field; used to set pos when appropriate pos receives the position of a field, when appropriate formatData the symbols for this formatter

UNKNOWN: ICU 2.0

subFormat

protected void subFormat(StringBuffer buf, char ch, int count, int beginOffset, FieldPosition pos, Calendar cal)
Format a single field; useFastFormat variant. Reuses a StringBuffer for results instead of creating a String on the heap for each call. NOTE We don't really need the beginOffset parameter, EXCEPT for the need to support the slow subFormat variant (above) which has to pass it in to us. TODO make this API public

UNKNOWN:

subParse

protected int subParse(String text, int start, char ch, int count, boolean obeyCount, boolean allowNegative, boolean[] ambiguousYear, Calendar cal)
Protected method that converts one field of the input string into a numeric field value in cal. Returns -start (for ParsePosition) if failed. Subclasses may override this method to modify or add parsing capabilities.

Parameters: text the time text to be parsed. start where to start parsing. ch the pattern character for the date field text to be parsed. count the count of a pattern character. obeyCount if true, then the next field directly abuts this one, and we should use the count to know when to stop parsing. ambiguousYear return parameter; upon return, if ambiguousYear[0] is true, then a two-digit year was parsed and may need to be readjusted.

Returns: the new start position if matching succeeded; a negative number indicating matching failure, otherwise. As a side effect, set the appropriate field of cal with the parsed value.

UNKNOWN: ICU 2.0

toLocalizedPattern

public String toLocalizedPattern()
Return a localized pattern string describing this date format.

UNKNOWN: ICU 2.0

toPattern

public String toPattern()
Return a pattern string describing this date format.

UNKNOWN: ICU 2.0

zeroPaddingNumber

protected void zeroPaddingNumber(StringBuffer buf, int value, int minDigits, int maxDigits)
Internal high-speed method. Reuses a StringBuffer for results instead of creating a String on the heap for each call.

UNKNOWN:

zeroPaddingNumber

protected String zeroPaddingNumber(long value, int minDigits, int maxDigits)
Formats a number with the specified minimum and maximum number of digits.

UNKNOWN: ICU 2.0

Copyright (c) 2006 IBM Corporation and others.