DateFormat is an abstract class for date/time formatting subclasses which
formats and parses dates or time in a language-independent manner.
The date/time formatting subclass, such as SimpleDateFormat, allows for
formatting (i.e., date -> text), parsing (text -> date), and
normalization. The date is represented as a
Date
object or
as the milliseconds since January 1, 1970, 00:00:00 GMT.
DateFormat provides many class methods for obtaining default date/time
formatters based on the default or a given locale and a number of formatting
styles. The formatting styles include FULL, LONG, MEDIUM, and SHORT. More
detail and examples of using these styles are provided in the method
descriptions.
DateFormat helps you to format and parse dates for any locale.
Your code can be completely independent of the locale conventions for
months, days of the week, or even the calendar format: lunar vs. solar.
To format a date for the current Locale, use one of the
static factory methods:
myString = DateFormat.getDateInstance().format(myDate);
If you are formatting multiple dates, it is
more efficient to get the format and use it multiple times so that
the system doesn't have to fetch the information about the local
language and country conventions multiple times.
DateFormat df = DateFormat.getDateInstance();
for (int i = 0; i < myDate.length; ++i) {
output.println(df.format(myDate[i]) + "; ");
}
To format a date for a different Locale, specify it in the
call to getDateInstance().
DateFormat df = DateFormat.getDateInstance(DateFormat.LONG, Locale.FRANCE);
You can use a DateFormat to parse also.
myDate = df.parse(myString);
Use getDateInstance to get the normal date format for that country.
There are other static factory methods available.
Use getTimeInstance to get the time format for that country.
Use getDateTimeInstance to get a date and time format. You can pass in
different options to these factory methods to control the length of the
result; from SHORT to MEDIUM to LONG to FULL. The exact result depends
on the locale, but generally:
- SHORT is completely numeric, such as 12.13.52 or 3:30pm
- MEDIUM is longer, such as Jan 12, 1952
- LONG is longer, such as January 12, 1952 or 3:30:32pm
- FULL is pretty completely specified, such as
Tuesday, April 12, 1952 AD or 3:30:42pm PST.
You can also set the time zone on the format if you wish.
If you want even more control over the format or parsing,
(or want to give your users more control),
you can try casting the DateFormat you get from the factory methods
to a SimpleDateFormat. This will work for the majority
of countries; just remember to put it in a try block in case you
encounter an unusual one.
You can also use forms of the parse and format methods with
ParsePosition and FieldPosition to
allow you to
- progressively parse through pieces of a string.
- align any particular field, or find out where it is for selection
on the screen.
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.