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Customizing Formats

The previous section, Using Predefined Formats, described the formatting styles provided by the DateFormat class. In most cases these predefined formats are adequate. However, if you want to create your own customized formats, you can use the SimpleDateFormat class.

The code examples that follow demonstrate the methods of the SimpleDateFormat class. You can find the full source code for the examples in the file named SimpleDateFormatDemo.

About Patterns

When you create a SimpleDateFormat object, you specify a pattern String. The contents of the pattern String determine the format of the date and time. For a full description of the pattern's syntax, see the tables in Date Format Pattern Syntax.

The following code formats a date and time according to the pattern String passed to the SimpleDateFormat constructor. The String returned by the format method contains the formatted date and time that are to be displayed.

Date today;
String output;
SimpleDateFormat formatter;

formatter = new SimpleDateFormat(pattern, currentLocale);
today = new Date();
output = formatter.format(today);
System.out.println(pattern + " " + output);

The following table shows the output generated by the previous code example when the U.S. Locale is specified:

Customized Date and Time Formats

Pattern	Output
dd.MM.yy	09.04.98
yyyy.MM.dd G 'at' hh:mm:ss z	1998.04.09 AD at 06:15:55 PDT
EEE, MMM d, ''yy	Thu, Apr 9, '98
h:mm a	6:15 PM
H:mm	18:15
H:mm:ss:SSS	18:15:55:624
K:mm a,z	6:15 PM,PDT
yyyy.MMMMM.dd GGG hh:mm aaa	1998.April.09 AD 06:15 PM

Patterns and Locale

The SimpleDateFormat class is locale-sensitive. If you instantiate SimpleDateFormat without a Locale parameter, it will format the date and time according to the default Locale. Both the pattern and the Locale determine the format. For the same pattern, SimpleDateFormat may format a date and time differently if the Locale varies.

In the example code that follows, the pattern is hardcoded in the statement that creates the SimpleDateFormat object:

Date today;
String result;
SimpleDateFormat formatter;

formatter = new SimpleDateFormat("EEE d MMM yy",
				 currentLocale);
today = new Date();
result = formatter.format(today);
System.out.println("Locale: " + currentLocale.toString());
System.out.println("Result: " + result);

When the currentLocale is set to different values, the preceding code example generates this output:

Locale: fr_FR
Result: ven 10 avr 98
Locale: de_DE
Result: Fr 10 Apr 98
Locale: en_US
Result: Thu 9 Apr 98

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