Calendar - java.util

Calendar

The abstract Calendar class provides a set of methods that allows you to convert a time in milliseconds to a number of useful components. Some examples of the type of information that can be provided are year, month, day, hour, minute, and second. It is intended that subclasses of Calendar will provide the specific functionality to interpret time information according to their own rules. This is one aspect of the Java class library that enables you to write programs that can operate in international environments. An example of such a subclass is GregorianCalendar.

Calendar provides no public constructors. Calendar defines several protected instance variables. areFieldsSet is a boolean that indicates if the time components have been set. fields is an array of ints that holds the components of the time. isSet is a boolean array that indicates if a specific time component has been set. time is a long that holds the current time for this object. isTimeSet is a boolean that indicates if the current time has been set.

A sampling of methods defined by Calendar are shown in Table 19-5.

Calendar defines the following int constants, which are used when you get or set components of the calendar. (The ones with the suffix FORMAT or STANDALONE were added by JDK 8.)

ALL_STYLES

AM

AM_PM

APRIL

AUGUST

DATE

DAY_OF_MONTH

DAY_OF_WEEK

DAY_OF_WEEK_IN_MONTH

DAY_OF_YEAR

DECEMBER

DST_OFFSET

ERA

FEBRUARY

FIELD_COUNT

FRIDAY

HOUR

HOUR_OF_DAY

JANUARY

JULY

JUNE

LONG

LONG_FORMAT

LONG_STANDALONE

MARCH

MAY

MILLISECOND

MINUTE

MONDAY

MONTH

NARROW_FORMAT

NARROW_STANDALONE

NOVEMBER

OCTOBER

PM

SATURDAY

SECOND

SEPTEMBER

SHORT

SHORT_FORMAT

SHORT_STANDALONE

SUNDAY

THURSDAY

TUESDAY

UNDECIMBER

WEDNESDAY

WEEK_OF_MONTH

WEEK_OF_YEAR

YEAR

ZONE_OFFSET

The following program demonstrates several Calendar methods:

// Demonstrate Calendar

import java.util.Calendar;

class CalendarDemo {

public static void main(String args[]) {

String months[]   = {

"Jan",        "Feb", "Mar", "Apr",

"May",       "Jun", "Jul", "Aug",

"Sep",        "Oct", "Nov", "Dec"};

    Create a calendar initialized with the

    current date and time in the default

    locale and timezone.

Calendar calendar = Calendar.getInstance();

// Display current time and date information.

System.out.print("Date: ");

System.out.print(months[calendar.get(Calendar.MONTH)]);

System.out.print(" " + calendar.get(Calendar.DATE) + " ");

System.out.println(calendar.get(Calendar.YEAR));

System.out.print("Time: ");

System.out.print(calendar.get(Calendar.HOUR) + ":");

System.out.print(calendar.get(Calendar.MINUTE) + ":");

System.out.println(calendar.get(Calendar.SECOND));

// Set the time and date information and display it.

 calendar.set(Calendar.HOUR, 10);

calendar.set(Calendar.MINUTE, 29);

calendar.set(Calendar.SECOND, 22);

 System.out.print("Updated time: ");

System.out.print(calendar.get(Calendar.HOUR) + ":");

System.out.print(calendar.get(Calendar.MINUTE) + ":");

System.out.println(calendar.get(Calendar.SECOND));

}

}

Sample output is shown here:

Date: Jan 1 2014

Time: 11:29:39

Updated time: 10:29:22