implements Serializable Cloneable Comparable<Calendar>
Known Direct Subclasses |
The Calendar
class is an abstract class that provides methods
for converting between a specific instant in time and a set of calendar fields
such as YEAR
, MONTH
,
DAY_OF_MONTH
, HOUR
, and so on, and for
manipulating the calendar fields, such as getting the date of the next
week. An instant in time can be represented by a millisecond value that is
an offset from the Epoch, January 1, 1970
00:00:00.000 GMT (Gregorian).
The class also provides additional fields and methods for
implementing a concrete calendar system outside the package. Those
fields and methods are defined as protected
.
Like other locale-sensitive classes, Calendar
provides a
class method, getInstance
, for getting a generally useful
object of this type. Calendar
's getInstance
method
returns a Calendar
object whose
calendar fields have been initialized with the current date and time:
Calendar rightNow = Calendar.getInstance();
A Calendar
object can produce all the calendar field values
needed to implement the date-time formatting for a particular language and
calendar style (for example, Japanese-Gregorian, Japanese-Traditional).
Calendar
defines the range of values returned by
certain calendar fields, as well as their meaning. For example,
the first month of the calendar system has value MONTH ==
JANUARY
for all calendars. Other values are defined by the
concrete subclass, such as ERA
. See individual field
documentation and subclass documentation for details.
Getting and Setting Calendar Field Values
The calendar field values can be set by calling the set
methods. Any field values set in a Calendar
will not be
interpreted until it needs to calculate its time value (milliseconds from
the Epoch) or values of the calendar fields. Calling the
get
, getTimeInMillis
, getTime
,
add
and roll
involves such calculation.
Leniency
Calendar
has two modes for interpreting the calendar
fields, lenient and non-lenient. When a
Calendar
is in lenient mode, it accepts a wider range of
calendar field values than it produces. When a Calendar
recomputes calendar field values for return by get()
, all of
the calendar fields are normalized. For example, a lenient
GregorianCalendar
interprets MONTH == JANUARY
,
DAY_OF_MONTH == 32
as February 1.
When a Calendar
is in non-lenient mode, it throws an
exception if there is any inconsistency in its calendar fields. For
example, a GregorianCalendar
always produces
DAY_OF_MONTH
values between 1 and the length of the month. A
non-lenient GregorianCalendar
throws an exception upon
calculating its time or calendar field values if any out-of-range field
value has been set.
First Week
Calendar
defines a locale-specific seven day week using two
parameters: the first day of the week and the minimal days in first week
(from 1 to 7). These numbers are taken from the locale resource data when a
Calendar
is constructed. They may also be specified explicitly
through the methods for setting their values.
When setting or getting the WEEK_OF_MONTH
or
WEEK_OF_YEAR
fields, Calendar
must determine the
first week of the month or year as a reference point. The first week of a
month or year is defined as the earliest seven day period beginning on
getFirstDayOfWeek()
and containing at least
getMinimalDaysInFirstWeek()
days of that month or year. Weeks
numbered ..., -1, 0 precede the first week; weeks numbered 2, 3,... follow
it. Note that the normalized numbering returned by get()
may be
different. For example, a specific Calendar
subclass may
designate the week before week 1 of a year as week n
of
the previous year.
Calendar Fields Resolution
When computing a date and time from the calendar fields, there may be insufficient information for the computation (such as only year and month with no day of month), or there may be inconsistent information (such as Tuesday, July 15, 1996 (Gregorian) -- July 15, 1996 is actually a Monday).Calendar
will resolve
calendar field values to determine the date and time in the
following way.
If there is any conflict in calendar field values,
Calendar
gives priorities to calendar fields that have been set
more recently. The following are the default combinations of the
calendar fields. The most recent combination, as determined by the
most recently set single field, will be used.
For the time of day fields: YEAR + MONTH + DAY_OF_MONTH YEAR + MONTH + WEEK_OF_MONTH + DAY_OF_WEEK YEAR + MONTH + DAY_OF_WEEK_IN_MONTH + DAY_OF_WEEK YEAR + DAY_OF_YEAR YEAR + DAY_OF_WEEK + WEEK_OF_YEAR
HOUR_OF_DAY AM_PM + HOUR
If there are any calendar fields whose values haven't been set in the selected
field combination, Calendar
uses their default values. The default
value of each field may vary by concrete calendar systems. For example, in
GregorianCalendar
, the default of a field is the same as that
of the start of the Epoch: i.e., YEAR = 1970
, MONTH =
JANUARY
, DAY_OF_MONTH = 1
, etc.
Note: There are certain possible ambiguities in interpretation of certain singular times, which are resolved in the following ways:
- 23:59 is the last minute of the day and 00:00 is the first minute of the next day. Thus, 23:59 on Dec 31, 1999 < 00:00 on Jan 1, 2000 < 00:01 on Jan 1, 2000.
- Although historically not precise, midnight also belongs to "am", and noon belongs to "pm", so on the same day, 12:00 am (midnight) < 12:01 am, and 12:00 pm (noon) < 12:01 pm
The date or time format strings are not part of the definition of a
calendar, as those must be modifiable or overridable by the user at
runtime. Use DateFormat
to format dates.
Field Manipulation
The calendar fields can be changed using three methods:set()
, add()
, and roll()
.
set(f, value)
changes calendar field
f
to value
. In addition, it sets an
internal member variable to indicate that calendar field f
has
been changed. Although calendar field f
is changed immediately,
the calendar's time value in milliseconds is not recomputed until the next call to
get()
, getTime()
, getTimeInMillis()
,
add()
, or roll()
is made. Thus, multiple calls to
set()
do not trigger multiple, unnecessary
computations. As a result of changing a calendar field using
set()
, other calendar fields may also change, depending on the
calendar field, the calendar field value, and the calendar system. In addition,
get(f)
will not necessarily return value
set by
the call to the set
method
after the calendar fields have been recomputed. The specifics are determined by
the concrete calendar class.
Example: Consider a GregorianCalendar
originally set to August 31, 1999. Calling set(Calendar.MONTH,
Calendar.SEPTEMBER)
sets the date to September 31,
1999. This is a temporary internal representation that resolves to
October 1, 1999 if getTime()
is then called. However, a
call to set(Calendar.DAY_OF_MONTH, 30)
before the call to
getTime()
sets the date to September 30, 1999, since
no recomputation occurs after set()
itself.
add(f, delta)
adds delta
to field f
. This is equivalent to calling set(f,
get(f) + delta)
with two adjustments:
Add rule 1. The value of field
f
after the call minus the value of fieldf
before the call isdelta
, modulo any overflow that has occurred in fieldf
. Overflow occurs when a field value exceeds its range and, as a result, the next larger field is incremented or decremented and the field value is adjusted back into its range.Add rule 2. If a smaller field is expected to be invariant, but it is impossible for it to be equal to its prior value because of changes in its minimum or maximum after field
f
is changed or other constraints, such as time zone offset changes, then its value is adjusted to be as close as possible to its expected value. A smaller field represents a smaller unit of time.HOUR
is a smaller field thanDAY_OF_MONTH
. No adjustment is made to smaller fields that are not expected to be invariant. The calendar system determines what fields are expected to be invariant.
In addition, unlike set()
, add()
forces
an immediate recomputation of the calendar's milliseconds and all
fields.
Example: Consider a GregorianCalendar
originally set to August 31, 1999. Calling add(Calendar.MONTH,
13)
sets the calendar to September 30, 2000. Add rule
1 sets the MONTH
field to September, since
adding 13 months to August gives September of the next year. Since
DAY_OF_MONTH
cannot be 31 in September in a
GregorianCalendar
, add rule 2 sets the
DAY_OF_MONTH
to 30, the closest possible value. Although
it is a smaller field, DAY_OF_WEEK
is not adjusted by
rule 2, since it is expected to change when the month changes in a
GregorianCalendar
.
roll(f, delta)
adds
delta
to field f
without changing larger
fields. This is equivalent to calling add(f, delta)
with
the following adjustment:
Roll rule. Larger fields are unchanged after the call. A larger field represents a larger unit of time.
DAY_OF_MONTH
is a larger field thanHOUR
.
Example: See GregorianCalendar.roll(int, int)
.
Usage model. To motivate the behavior of
add()
and roll()
, consider a user interface
component with increment and decrement buttons for the month, day, and
year, and an underlying GregorianCalendar
. If the
interface reads January 31, 1999 and the user presses the month
increment button, what should it read? If the underlying
implementation uses set()
, it might read March 3, 1999. A
better result would be February 28, 1999. Furthermore, if the user
presses the month increment button again, it should read March 31,
1999, not March 28, 1999. By saving the original date and using either
add()
or roll()
, depending on whether larger
fields should be affected, the user interface can behave as most users
will intuitively expect.
Nested Class Summary
class | Calendar.Builder | Calendar.Builder is used for creating a Calendar from
various date-time parameters. |
Constant Summary
int | ALL_STYLES | A style specifier for getDisplayNames indicating names in all styles, such as
"January" and "Jan". |
int | AM | Value of the AM_PM field indicating the
period of the day from midnight to just before noon. |
int | AM_PM | Field number for get and set indicating
whether the HOUR is before or after noon. |
int | APRIL | Value of the MONTH field indicating the
fourth month of the year in the Gregorian and Julian calendars. |
int | AUGUST | Value of the MONTH field indicating the
eighth month of the year in the Gregorian and Julian calendars. |
int | DATE | Field number for get and set indicating the
day of the month. |
int | DAY_OF_MONTH | Field number for get and set indicating the
day of the month. |
int | DAY_OF_WEEK | Field number for get and set indicating the day
of the week. |
int | DAY_OF_WEEK_IN_MONTH | Field number for get and set indicating the
ordinal number of the day of the week within the current month. |
int | DAY_OF_YEAR | Field number for get and set indicating the day
number within the current year. |
int | DECEMBER | Value of the MONTH field indicating the
twelfth month of the year in the Gregorian and Julian calendars. |
int | DST_OFFSET | Field number for get and set indicating the
daylight saving offset in milliseconds. |
int | ERA | Field number for get and set indicating the
era, e.g., AD or BC in the Julian calendar. |
int | FEBRUARY | Value of the MONTH field indicating the
second month of the year in the Gregorian and Julian calendars. |
int | FIELD_COUNT | The number of distinct fields recognized by get and set . |
int | FRIDAY | Value of the DAY_OF_WEEK field indicating
Friday. |
int | HOUR | Field number for get and set indicating the
hour of the morning or afternoon. |
int | HOUR_OF_DAY | Field number for get and set indicating the
hour of the day. |
int | JANUARY | Value of the MONTH field indicating the
first month of the year in the Gregorian and Julian calendars. |
int | JULY | Value of the MONTH field indicating the
seventh month of the year in the Gregorian and Julian calendars. |
int | JUNE | Value of the MONTH field indicating the
sixth month of the year in the Gregorian and Julian calendars. |
int | LONG | A style specifier for getDisplayName and getDisplayNames equivalent to LONG_FORMAT . |
int | LONG_FORMAT | A style specifier for getDisplayName and getDisplayNames indicating a long name used for format. |
int | LONG_STANDALONE | A style specifier for getDisplayName and getDisplayNames indicating a long name used independently,
such as a month name as calendar headers. |
int | MARCH | Value of the MONTH field indicating the
third month of the year in the Gregorian and Julian calendars. |
int | MAY | Value of the MONTH field indicating the
fifth month of the year in the Gregorian and Julian calendars. |
int | MILLISECOND | Field number for get and set indicating the
millisecond within the second. |
int | MINUTE | Field number for get and set indicating the
minute within the hour. |
int | MONDAY | Value of the DAY_OF_WEEK field indicating
Monday. |
int | MONTH | Field number for get and set indicating the
month. |
int | NARROW_FORMAT | A style specifier for getDisplayName and getDisplayNames indicating a narrow name used for format. |
int | NARROW_STANDALONE | A style specifier for getDisplayName and getDisplayNames indicating a narrow name independently. |
int | NOVEMBER | Value of the MONTH field indicating the
eleventh month of the year in the Gregorian and Julian calendars. |
int | OCTOBER | Value of the MONTH field indicating the
tenth month of the year in the Gregorian and Julian calendars. |
int | PM | Value of the AM_PM field indicating the
period of the day from noon to just before midnight. |
int | SATURDAY | Value of the DAY_OF_WEEK field indicating
Saturday. |
int | SECOND | Field number for get and set indicating the
second within the minute. |
int | SEPTEMBER | Value of the MONTH field indicating the
ninth month of the year in the Gregorian and Julian calendars. |
int | SHORT | A style specifier for getDisplayName and getDisplayNames equivalent to SHORT_FORMAT . |
int | SHORT_FORMAT | A style specifier for getDisplayName and getDisplayNames indicating a short name used for format. |
int | SHORT_STANDALONE | A style specifier for getDisplayName and getDisplayNames indicating a short name used independently,
such as a month abbreviation as calendar headers. |
int | SUNDAY | Value of the DAY_OF_WEEK field indicating
Sunday. |
int | THURSDAY | Value of the DAY_OF_WEEK field indicating
Thursday. |
int | TUESDAY | Value of the DAY_OF_WEEK field indicating
Tuesday. |
int | UNDECIMBER | Value of the MONTH field indicating the
thirteenth month of the year. |
int | WEDNESDAY | Value of the DAY_OF_WEEK field indicating
Wednesday. |
int | WEEK_OF_MONTH | Field number for get and set indicating the
week number within the current month. |
int | WEEK_OF_YEAR | Field number for get and set indicating the
week number within the current year. |
int | YEAR | Field number for get and set indicating the
year. |
int | ZONE_OFFSET | Field number for get and set
indicating the raw offset from GMT in milliseconds. |
Field Summary
protected boolean | areFieldsSet | True if fields[] are in sync with the currently set time. |
protected int[] | fields | The calendar field values for the currently set time for this calendar. |
protected boolean[] | isSet | The flags which tell if a specified calendar field for the calendar is set. |
protected boolean | isTimeSet | True if then the value of time is valid. |
protected long | time | The currently set time for this calendar, expressed in milliseconds after January 1, 1970, 0:00:00 GMT. |
Protected Constructor Summary
Public Method Summary
abstract void |
add(int field, int amount)
Adds or subtracts the specified amount of time to the given calendar field,
based on the calendar's rules.
|
boolean | |
boolean | |
final void | |
final void | |
Object |
clone()
Creates and returns a copy of this object.
|
int | |
boolean | |
int |
get(int field)
Returns the value of the given calendar field.
|
int |
getActualMaximum(int field)
Returns the maximum value that the specified calendar field
could have, given the time value of this
Calendar . |
int |
getActualMinimum(int field)
Returns the minimum value that the specified calendar field
could have, given the time value of this
Calendar . |
static Set<String> |
getAvailableCalendarTypes()
Returns an unmodifiable
Set containing all calendar types
supported by Calendar in the runtime environment. |
synchronized static Locale[] |
getAvailableLocales()
Returns an array of all locales for which the
getInstance
methods of this class can return localized instances. |
String |
getCalendarType()
Returns the calendar type of this
Calendar . |
String |
getDisplayName(int field, int style, Locale locale)
Returns the string representation of the calendar
field value in the given style and
locale . |
Map<String, Integer> |
getDisplayNames(int field, int style, Locale locale)
Returns a
Map containing all names of the calendar
field in the given style and
locale and their corresponding field values. |
int |
getFirstDayOfWeek()
Gets what the first day of the week is; e.g.,
SUNDAY in the U.S.,
MONDAY in France. |
abstract int |
getGreatestMinimum(int field)
Returns the highest minimum value for the given calendar field
of this
Calendar instance. |
static Calendar |
getInstance()
Gets a calendar using the default time zone and locale.
|
static Calendar | |
static Calendar | |
static Calendar | |
abstract int |
getLeastMaximum(int field)
Returns the lowest maximum value for the given calendar field
of this
Calendar instance. |
abstract int |
getMaximum(int field)
Returns the maximum value for the given calendar field of this
Calendar instance. |
int |
getMinimalDaysInFirstWeek()
Gets what the minimal days required in the first week of the year are;
e.g., if the first week is defined as one that contains the first day
of the first month of a year, this method returns 1.
|
abstract int |
getMinimum(int field)
Returns the minimum value for the given calendar field of this
Calendar instance. |
final Date | |
long |
getTimeInMillis()
Returns this Calendar's time value in milliseconds.
|
TimeZone |
getTimeZone()
Gets the time zone.
|
int |
getWeekYear()
Returns the week year represented by this
Calendar . |
int |
getWeeksInWeekYear()
Returns the number of weeks in the week year represented by this
Calendar . |
int |
hashCode()
Returns a hash code for this calendar.
|
boolean |
isLenient()
Tells whether date/time interpretation is to be lenient.
|
final boolean |
isSet(int field)
Determines if the given calendar field has a value set,
including cases that the value has been set by internal fields
calculations triggered by a
get method call. |
boolean |
isWeekDateSupported()
Returns whether this
Calendar supports week dates. |
abstract void |
roll(int field, boolean up)
Adds or subtracts (up/down) a single unit of time on the given time
field without changing larger fields.
|
void |
roll(int field, int amount)
Adds the specified (signed) amount to the specified calendar field
without changing larger fields.
|
final void |
set(int year, int month, int date, int hourOfDay, int minute, int second)
Sets the values for the fields
YEAR , MONTH ,
DAY_OF_MONTH , HOUR_OF_DAY , MINUTE , and
SECOND . |
final void |
set(int year, int month, int date, int hourOfDay, int minute)
Sets the values for the calendar fields
YEAR ,
MONTH , DAY_OF_MONTH ,
HOUR_OF_DAY , and MINUTE . |
void |
set(int field, int value)
Sets the given calendar field to the given value.
|
final void |
set(int year, int month, int date)
Sets the values for the calendar fields
YEAR ,
MONTH , and DAY_OF_MONTH . |
void |
setFirstDayOfWeek(int value)
Sets what the first day of the week is; e.g.,
SUNDAY in the U.S.,
MONDAY in France. |
void |
setLenient(boolean lenient)
Specifies whether or not date/time interpretation is to be lenient.
|
void |
setMinimalDaysInFirstWeek(int value)
Sets what the minimal days required in the first week of the year are;
For example, if the first week is defined as one that contains the first
day of the first month of a year, call this method with value 1.
|
final void | |
void |
setTimeInMillis(long millis)
Sets this Calendar's current time from the given long value.
|
void | |
void |
setWeekDate(int weekYear, int weekOfYear, int dayOfWeek)
Sets the date of this
Calendar with the the given date
specifiers - week year, week of year, and day of week. |
String |
toString()
Return a string representation of this calendar.
|
Protected Method Summary
void |
complete()
Fills in any unset fields in the calendar fields.
|
abstract void | |
abstract void | |
final int |
internalGet(int field)
Returns the value of the given calendar field.
|
Inherited Method Summary
Constants
public static final int ALL_STYLES
A style specifier for getDisplayNames
indicating names in all styles, such as
"January" and "Jan".
public static final int AM
Value of the AM_PM
field indicating the
period of the day from midnight to just before noon.
public static final int AM_PM
public static final int APRIL
Value of the MONTH
field indicating the
fourth month of the year in the Gregorian and Julian calendars.
public static final int AUGUST
Value of the MONTH
field indicating the
eighth month of the year in the Gregorian and Julian calendars.
public static final int DATE
Field number for get
and set
indicating the
day of the month. This is a synonym for DAY_OF_MONTH
.
The first day of the month has value 1.
See Also
public static final int DAY_OF_MONTH
Field number for get
and set
indicating the
day of the month. This is a synonym for DATE
.
The first day of the month has value 1.
See Also
public static final int DAY_OF_WEEK
public static final int DAY_OF_WEEK_IN_MONTH
Field number for get
and set
indicating the
ordinal number of the day of the week within the current month. Together
with the DAY_OF_WEEK
field, this uniquely specifies a day
within a month. Unlike WEEK_OF_MONTH
and
WEEK_OF_YEAR
, this field's value does not depend on
getFirstDayOfWeek()
or
getMinimalDaysInFirstWeek()
. DAY_OF_MONTH 1
through 7
always correspond to DAY_OF_WEEK_IN_MONTH
1
; 8
through 14
correspond to
DAY_OF_WEEK_IN_MONTH 2
, and so on.
DAY_OF_WEEK_IN_MONTH 0
indicates the week before
DAY_OF_WEEK_IN_MONTH 1
. Negative values count back from the
end of the month, so the last Sunday of a month is specified as
DAY_OF_WEEK = SUNDAY, DAY_OF_WEEK_IN_MONTH = -1
. Because
negative values count backward they will usually be aligned differently
within the month than positive values. For example, if a month has 31
days, DAY_OF_WEEK_IN_MONTH -1
will overlap
DAY_OF_WEEK_IN_MONTH 5
and the end of 4
.
See Also
public static final int DAY_OF_YEAR
Field number for get
and set
indicating the day
number within the current year. The first day of the year has value 1.
public static final int DECEMBER
Value of the MONTH
field indicating the
twelfth month of the year in the Gregorian and Julian calendars.
public static final int DST_OFFSET
Field number for get
and set
indicating the
daylight saving offset in milliseconds.
This field reflects the correct daylight saving offset value of
the time zone of this Calendar
if the
TimeZone
implementation subclass supports
historical Daylight Saving Time schedule changes.
public static final int ERA
Field number for get
and set
indicating the
era, e.g., AD or BC in the Julian calendar. This is a calendar-specific
value; see subclass documentation.
public static final int FEBRUARY
Value of the MONTH
field indicating the
second month of the year in the Gregorian and Julian calendars.
public static final int FIELD_COUNT
The number of distinct fields recognized by get
and set
.
Field numbers range from 0..FIELD_COUNT-1
.
public static final int HOUR
Field number for get
and set
indicating the
hour of the morning or afternoon. HOUR
is used for the
12-hour clock (0 - 11). Noon and midnight are represented by 0, not by 12.
E.g., at 10:04:15.250 PM the HOUR
is 10.
See Also
public static final int HOUR_OF_DAY
Field number for get
and set
indicating the
hour of the day. HOUR_OF_DAY
is used for the 24-hour clock.
E.g., at 10:04:15.250 PM the HOUR_OF_DAY
is 22.
See Also
public static final int JANUARY
Value of the MONTH
field indicating the
first month of the year in the Gregorian and Julian calendars.
public static final int JULY
Value of the MONTH
field indicating the
seventh month of the year in the Gregorian and Julian calendars.
public static final int JUNE
Value of the MONTH
field indicating the
sixth month of the year in the Gregorian and Julian calendars.
public static final int LONG
A style specifier for getDisplayName
and getDisplayNames
equivalent to LONG_FORMAT
.
See Also
public static final int LONG_FORMAT
A style specifier for getDisplayName
and getDisplayNames
indicating a long name used for format.
public static final int LONG_STANDALONE
A style specifier for getDisplayName
and getDisplayNames
indicating a long name used independently,
such as a month name as calendar headers.
public static final int MARCH
Value of the MONTH
field indicating the
third month of the year in the Gregorian and Julian calendars.
public static final int MAY
Value of the MONTH
field indicating the
fifth month of the year in the Gregorian and Julian calendars.
public static final int MILLISECOND
Field number for get
and set
indicating the
millisecond within the second.
E.g., at 10:04:15.250 PM the MILLISECOND
is 250.
public static final int MINUTE
Field number for get
and set
indicating the
minute within the hour.
E.g., at 10:04:15.250 PM the MINUTE
is 4.
public static final int MONTH
Field number for get
and set
indicating the
month. This is a calendar-specific value. The first month of
the year in the Gregorian and Julian calendars is
JANUARY
which is 0; the last depends on the number
of months in a year.
public static final int NARROW_FORMAT
A style specifier for getDisplayName
and getDisplayNames
indicating a narrow name used for format. Narrow names
are typically single character strings, such as "M" for Monday.
public static final int NARROW_STANDALONE
A style specifier for getDisplayName
and getDisplayNames
indicating a narrow name independently. Narrow names
are typically single character strings, such as "M" for Monday.
public static final int NOVEMBER
Value of the MONTH
field indicating the
eleventh month of the year in the Gregorian and Julian calendars.
public static final int OCTOBER
Value of the MONTH
field indicating the
tenth month of the year in the Gregorian and Julian calendars.
public static final int PM
Value of the AM_PM
field indicating the
period of the day from noon to just before midnight.
public static final int SATURDAY
Value of the DAY_OF_WEEK
field indicating
Saturday.
public static final int SECOND
Field number for get
and set
indicating the
second within the minute.
E.g., at 10:04:15.250 PM the SECOND
is 15.
public static final int SEPTEMBER
Value of the MONTH
field indicating the
ninth month of the year in the Gregorian and Julian calendars.
public static final int SHORT
A style specifier for getDisplayName
and getDisplayNames
equivalent to SHORT_FORMAT
.
See Also
public static final int SHORT_FORMAT
A style specifier for getDisplayName
and getDisplayNames
indicating a short name used for format.
public static final int SHORT_STANDALONE
A style specifier for getDisplayName
and getDisplayNames
indicating a short name used independently,
such as a month abbreviation as calendar headers.
public static final int THURSDAY
Value of the DAY_OF_WEEK
field indicating
Thursday.
public static final int TUESDAY
Value of the DAY_OF_WEEK
field indicating
Tuesday.
public static final int UNDECIMBER
Value of the MONTH
field indicating the
thirteenth month of the year. Although GregorianCalendar
does not use this value, lunar calendars do.
public static final int WEDNESDAY
Value of the DAY_OF_WEEK
field indicating
Wednesday.
public static final int WEEK_OF_MONTH
Field number for get
and set
indicating the
week number within the current month. The first week of the month, as
defined by getFirstDayOfWeek()
and
getMinimalDaysInFirstWeek()
, has value 1. Subclasses define
the value of WEEK_OF_MONTH
for days before the first week of
the month.
public static final int WEEK_OF_YEAR
Field number for get
and set
indicating the
week number within the current year. The first week of the year, as
defined by getFirstDayOfWeek()
and
getMinimalDaysInFirstWeek()
, has value 1. Subclasses define
the value of WEEK_OF_YEAR
for days before the first week of
the year.
public static final int YEAR
Field number for get
and set
indicating the
year. This is a calendar-specific value; see subclass documentation.
public static final int ZONE_OFFSET
Field number for get
and set
indicating the raw offset from GMT in milliseconds.
This field reflects the correct GMT offset value of the time
zone of this Calendar
if the
TimeZone
implementation subclass supports
historical GMT offset changes.
Fields
protected boolean areFieldsSet
True if fields[]
are in sync with the currently set time.
If false, then the next attempt to get the value of a field will
force a recomputation of all fields from the current value of
time
.
protected int[] fields
The calendar field values for the currently set time for this calendar.
This is an array of FIELD_COUNT
integers, with index values
ERA
through DST_OFFSET
.
protected boolean[] isSet
The flags which tell if a specified calendar field for the calendar is set.
A new object has no fields set. After the first call to a method
which generates the fields, they all remain set after that.
This is an array of FIELD_COUNT
booleans, with index values
ERA
through DST_OFFSET
.
protected boolean isTimeSet
True if then the value of time
is valid.
The time is made invalid by a change to an item of field[]
.
See Also
protected long time
The currently set time for this calendar, expressed in milliseconds after January 1, 1970, 0:00:00 GMT.
See Also
Protected Constructors
protected Calendar ()
Constructs a Calendar with the default time zone
and the default FORMAT
locale.
See Also
Public Methods
public abstract void add (int field, int amount)
Adds or subtracts the specified amount of time to the given calendar field, based on the calendar's rules. For example, to subtract 5 days from the current time of the calendar, you can achieve it by calling:
add(Calendar.DAY_OF_MONTH, -5)
.
Parameters
field | the calendar field. |
---|---|
amount | the amount of date or time to be added to the field. |
See Also
public boolean after (Object when)
Returns whether this Calendar
represents a time
after the time represented by the specified
Object
. This method is equivalent to:
compareTo(when) > 0
when
is a Calendar
instance. Otherwise, the method returns false
.Parameters
when | the Object to be compared |
---|
Returns
true
if the time of thisCalendar
is after the time represented bywhen
;false
otherwise.
See Also
public boolean before (Object when)
Returns whether this Calendar
represents a time
before the time represented by the specified
Object
. This method is equivalent to:
compareTo(when) < 0
when
is a Calendar
instance. Otherwise, the method returns false
.Parameters
when | the Object to be compared |
---|
Returns
true
if the time of thisCalendar
is before the time represented bywhen
;false
otherwise.
See Also
public final void clear ()
Sets all the calendar field values and the time value
(millisecond offset from the Epoch) of
this Calendar
undefined. This means that isSet()
will return false
for all the
calendar fields, and the date and time calculations will treat
the fields as if they had never been set. A
Calendar
implementation class may use its specific
default field values for date/time calculations. For example,
GregorianCalendar
uses 1970 if the
YEAR
field value is undefined.
See Also
public final void clear (int field)
Sets the given calendar field value and the time value
(millisecond offset from the Epoch) of
this Calendar
undefined. This means that isSet(field)
will return false
, and
the date and time calculations will treat the field as if it
had never been set. A Calendar
implementation
class may use the field's specific default value for date and
time calculations.
The HOUR_OF_DAY
, HOUR
and AM_PM
fields are handled independently and the the resolution rule for the time of
day is applied. Clearing one of the fields doesn't reset
the hour of day value of this Calendar
. Use set(Calendar.HOUR_OF_DAY, 0)
to reset the hour
value.
Parameters
field | the calendar field to be cleared. |
---|
See Also
public int compareTo (Calendar anotherCalendar)
Compares the time values (millisecond offsets from the Epoch) represented by two
Calendar
objects.
Parameters
anotherCalendar | the Calendar to be compared. |
---|
Returns
- the value
0
if the time represented by the argument is equal to the time represented by thisCalendar
; a value less than0
if the time of thisCalendar
is before the time represented by the argument; and a value greater than0
if the time of thisCalendar
is after the time represented by the argument.
Throws
NullPointerException | if the specified Calendar is
null . |
---|---|
IllegalArgumentException | if the time value of the
specified Calendar object can't be obtained due to
any invalid calendar values. |
public boolean equals (Object obj)
Compares this Calendar
to the specified
Object
. The result is true
if and only if
the argument is a Calendar
object of the same calendar
system that represents the same time value (millisecond offset from the
Epoch) under the same
Calendar
parameters as this object.
The Calendar
parameters are the values represented
by the isLenient
, getFirstDayOfWeek
,
getMinimalDaysInFirstWeek
and getTimeZone
methods. If there is any difference in those parameters
between the two Calendar
s, this method returns
false
.
Use the compareTo
method to
compare only the time values.
Parameters
obj | the object to compare with. |
---|
Returns
true
if this object is equal toobj
;false
otherwise.
public int get (int field)
Returns the value of the given calendar field. In lenient mode,
all calendar fields are normalized. In non-lenient mode, all
calendar fields are validated and this method throws an
exception if any calendar fields have out-of-range values. The
normalization and validation are handled by the
complete()
method, which process is calendar
system dependent.
Parameters
field | the given calendar field. |
---|
Returns
- the value for the given calendar field.
Throws
ArrayIndexOutOfBoundsException | if the specified field is out of range
(field < 0 || field >= FIELD_COUNT ). |
---|
See Also
public int getActualMaximum (int field)
Returns the maximum value that the specified calendar field
could have, given the time value of this
Calendar
. For example, the actual maximum value of
the MONTH
field is 12 in some years, and 13 in
other years in the Hebrew calendar system.
The default implementation of this method uses an iterative algorithm to determine the actual maximum value for the calendar field. Subclasses should, if possible, override this with a more efficient implementation.
Parameters
field | the calendar field |
---|
Returns
- the maximum of the given calendar field for the time
value of this
Calendar
public int getActualMinimum (int field)
Returns the minimum value that the specified calendar field
could have, given the time value of this Calendar
.
The default implementation of this method uses an iterative
algorithm to determine the actual minimum value for the
calendar field. Subclasses should, if possible, override this
with a more efficient implementation - in many cases, they can
simply return getMinimum()
.
Parameters
field | the calendar field |
---|
Returns
- the minimum of the given calendar field for the time
value of this
Calendar
public static Set<String> getAvailableCalendarTypes ()
Returns an unmodifiable Set
containing all calendar types
supported by Calendar
in the runtime environment. The available
calendar types can be used for the Unicode locale extensions.
The Set
returned contains at least "gregory"
. The
calendar types don't include aliases, such as "gregorian"
for
"gregory"
.
Returns
- an unmodifiable
Set
containing all available calendar types
public static synchronized Locale[] getAvailableLocales ()
Returns an array of all locales for which the getInstance
methods of this class can return localized instances.
The array returned must contain at least a Locale
instance equal to Locale.US
.
Returns
- An array of locales for which localized
Calendar
instances are available.
public String getCalendarType ()
Returns the calendar type of this Calendar
. Calendar types are
defined by the Unicode Locale Data Markup Language (LDML)
specification.
The default implementation of this method returns the class name of
this Calendar
instance. Any subclasses that implement
LDML-defined calendar systems should override this method to return
appropriate calendar types.
Returns
- the LDML-defined calendar type or the class name of this
Calendar
instance
public String getDisplayName (int field, int style, Locale locale)
Returns the string representation of the calendar
field
value in the given style
and
locale
. If no string representation is
applicable, null
is returned. This method calls
get(field)
to get the calendar
field
value if the string representation is
applicable to the given calendar field
.
For example, if this Calendar
is a
GregorianCalendar
and its date is 2005-01-01, then
the string representation of the MONTH
field would be
"January" in the long style in an English locale or "Jan" in
the short style. However, no string representation would be
available for the DAY_OF_MONTH
field, and this method
would return null
.
The default implementation supports the calendar fields for
which a DateFormatSymbols
has names in the given
locale
.
Parameters
field | the calendar field for which the string representation is returned |
---|---|
style | the style applied to the string representation; one of SHORT_FORMAT (SHORT ), SHORT_STANDALONE ,
LONG_FORMAT (LONG ), LONG_STANDALONE ,
NARROW_FORMAT , or NARROW_STANDALONE . |
locale | the locale for the string representation
(any calendar types specified by locale are ignored) |
Returns
- the string representation of the given
field
in the givenstyle
, ornull
if no string representation is applicable.
Throws
IllegalArgumentException | if field or style is invalid,
or if this Calendar is non-lenient and any
of the calendar fields have invalid values |
---|---|
NullPointerException | if locale is null |
public Map<String, Integer> getDisplayNames (int field, int style, Locale locale)
Returns a Map
containing all names of the calendar
field
in the given style
and
locale
and their corresponding field values. For
example, if this Calendar
is a GregorianCalendar
, the returned map would contain "Jan" to
JANUARY
, "Feb" to FEBRUARY
, and so on, in the
{@linkplain #SHORT short} style in an English locale.
Narrow names may not be unique due to use of single characters,
such as "S" for Sunday and Saturday. In that case narrow names are not
included in the returned Map
.
The values of other calendar fields may be taken into
account to determine a set of display names. For example, if
this Calendar
is a lunisolar calendar system and
the year value given by the YEAR
field has a leap
month, this method would return month names containing the leap
month name, and month names are mapped to their values specific
for the year.
The default implementation supports display names contained in
a DateFormatSymbols
. For example, if field
is MONTH
and style
is ALL_STYLES
, this method returns a Map
containing
all strings returned by DateFormatSymbols.getShortMonths()
and DateFormatSymbols.getMonths()
.
Parameters
field | the calendar field for which the display names are returned |
---|---|
style | the style applied to the string representation; one of SHORT_FORMAT (SHORT ), SHORT_STANDALONE ,
LONG_FORMAT (LONG ), LONG_STANDALONE ,
NARROW_FORMAT , or NARROW_STANDALONE |
locale | the locale for the display names |
Returns
- a
Map
containing all display names instyle
andlocale
and their field values, ornull
if no display names are defined forfield
Throws
IllegalArgumentException | if field or style is invalid,
or if this Calendar is non-lenient and any
of the calendar fields have invalid values |
---|---|
NullPointerException | if locale is null |
public int getFirstDayOfWeek ()
Gets what the first day of the week is; e.g., SUNDAY
in the U.S.,
MONDAY
in France.
Returns
- the first day of the week.
public abstract int getGreatestMinimum (int field)
Returns the highest minimum value for the given calendar field
of this Calendar
instance. The highest minimum
value is defined as the largest value returned by getActualMinimum(int)
for any possible time value. The
greatest minimum value depends on calendar system specific
parameters of the instance.
Parameters
field | the calendar field. |
---|
Returns
- the highest minimum value for the given calendar field.
public static Calendar getInstance ()
Gets a calendar using the default time zone and locale. The
Calendar
returned is based on the current time
in the default time zone with the default
FORMAT
locale.
Returns
- a Calendar.
public static Calendar getInstance (Locale aLocale)
Gets a calendar using the default time zone and specified locale.
The Calendar
returned is based on the current time
in the default time zone with the given locale.
Parameters
aLocale | the locale for the week data |
---|
Returns
- a Calendar.
public static Calendar getInstance (TimeZone zone, Locale aLocale)
Gets a calendar with the specified time zone and locale.
The Calendar
returned is based on the current time
in the given time zone with the given locale.
Parameters
zone | the time zone to use |
---|---|
aLocale | the locale for the week data |
Returns
- a Calendar.
public static Calendar getInstance (TimeZone zone)
Gets a calendar using the specified time zone and default locale.
The Calendar
returned is based on the current time
in the given time zone with the default
FORMAT
locale.
Parameters
zone | the time zone to use |
---|
Returns
- a Calendar.
public abstract int getLeastMaximum (int field)
Returns the lowest maximum value for the given calendar field
of this Calendar
instance. The lowest maximum
value is defined as the smallest value returned by getActualMaximum(int)
for any possible time value. The least
maximum value depends on calendar system specific parameters of
the instance. For example, a Calendar
for the
Gregorian calendar system returns 28 for the
DAY_OF_MONTH
field, because the 28th is the last
day of the shortest month of this calendar, February in a
common year.
Parameters
field | the calendar field. |
---|
Returns
- the lowest maximum value for the given calendar field.
public abstract int getMaximum (int field)
Returns the maximum value for the given calendar field of this
Calendar
instance. The maximum value is defined as
the largest value returned by the get
method
for any possible time value. The maximum value depends on
calendar system specific parameters of the instance.
Parameters
field | the calendar field. |
---|
Returns
- the maximum value for the given calendar field.
public int getMinimalDaysInFirstWeek ()
Gets what the minimal days required in the first week of the year are; e.g., if the first week is defined as one that contains the first day of the first month of a year, this method returns 1. If the minimal days required must be a full week, this method returns 7.
Returns
- the minimal days required in the first week of the year.
See Also
public abstract int getMinimum (int field)
Returns the minimum value for the given calendar field of this
Calendar
instance. The minimum value is defined as
the smallest value returned by the get
method
for any possible time value. The minimum value depends on
calendar system specific parameters of the instance.
Parameters
field | the calendar field. |
---|
Returns
- the minimum value for the given calendar field.
public final Date getTime ()
Returns a Date
object representing this
Calendar
's time value (millisecond offset from the Epoch").
Returns
- a
Date
representing the time value.
See Also
public long getTimeInMillis ()
Returns this Calendar's time value in milliseconds.
Returns
- the current time as UTC milliseconds from the epoch.
See Also
public TimeZone getTimeZone ()
Gets the time zone.
Returns
- the time zone object associated with this calendar.
public int getWeekYear ()
Returns the week year represented by this Calendar
. The
week year is in sync with the week cycle. The {@linkplain #getFirstDayOfWeek() first day of the first week} is the first
day of the week year.
The default implementation of this method throws an
UnsupportedOperationException
.
Returns
- the week year of this
Calendar
Throws
UnsupportedOperationException | if any week year numbering isn't supported
in this Calendar . |
---|
public int getWeeksInWeekYear ()
Returns the number of weeks in the week year represented by this
Calendar
.
The default implementation of this method throws an
UnsupportedOperationException
.
Returns
- the number of weeks in the week year.
Throws
UnsupportedOperationException | if any week year numbering isn't supported in this
Calendar . |
---|
public int hashCode ()
Returns a hash code for this calendar.
Returns
- a hash code value for this object.
public boolean isLenient ()
Tells whether date/time interpretation is to be lenient.
Returns
true
if the interpretation mode of this calendar is lenient;false
otherwise.
See Also
public final boolean isSet (int field)
Determines if the given calendar field has a value set,
including cases that the value has been set by internal fields
calculations triggered by a get
method call.
Parameters
field | the calendar field to test |
---|
Returns
true
if the given calendar field has a value set;false
otherwise.
public boolean isWeekDateSupported ()
Returns whether this Calendar
supports week dates.
The default implementation of this method returns false
.
Returns
true
if thisCalendar
supports week dates;false
otherwise.
public abstract void roll (int field, boolean up)
Adds or subtracts (up/down) a single unit of time on the given time field without changing larger fields. For example, to roll the current date up by one day, you can achieve it by calling:
roll(Calendar.DATE, true).
When rolling on the year or Calendar.YEAR field, it will roll the year
value in the range between 1 and the value returned by calling
getMaximum(Calendar.YEAR)
.
When rolling on the month or Calendar.MONTH field, other fields like
date might conflict and, need to be changed. For instance,
rolling the month on the date 01/31/96 will result in 02/29/96.
When rolling on the hour-in-day or Calendar.HOUR_OF_DAY field, it will
roll the hour value in the range between 0 and 23, which is zero-based.
Parameters
field | the time field. |
---|---|
up | indicates if the value of the specified time field is to be rolled up or rolled down. Use true if rolling up, false otherwise. |
See Also
public void roll (int field, int amount)
Adds the specified (signed) amount to the specified calendar field without changing larger fields. A negative amount means to roll down.
NOTE: This default implementation on Calendar
just repeatedly calls the
version of roll()
that rolls by one unit. This may not
always do the right thing. For example, if the DAY_OF_MONTH
field is 31,
rolling through February will leave it set to 28. The GregorianCalendar
version of this function takes care of this problem. Other subclasses
should also provide overrides of this function that do the right thing.
Parameters
field | the calendar field. |
---|---|
amount | the signed amount to add to the calendar field . |
public final void set (int year, int month, int date, int hourOfDay, int minute, int second)
Sets the values for the fields YEAR
, MONTH
,
DAY_OF_MONTH
, HOUR_OF_DAY
, MINUTE
, and
SECOND
.
Previous values of other fields are retained. If this is not desired,
call clear()
first.
Parameters
year | the value used to set the YEAR calendar field. |
---|---|
month | the value used to set the MONTH calendar field.
Month value is 0-based. e.g., 0 for January. |
date | the value used to set the DAY_OF_MONTH calendar field. |
hourOfDay | the value used to set the HOUR_OF_DAY calendar field. |
minute | the value used to set the MINUTE calendar field. |
second | the value used to set the SECOND calendar field. |
public final void set (int year, int month, int date, int hourOfDay, int minute)
Sets the values for the calendar fields YEAR
,
MONTH
, DAY_OF_MONTH
,
HOUR_OF_DAY
, and MINUTE
.
Previous values of other fields are retained. If this is not desired,
call clear()
first.
Parameters
year | the value used to set the YEAR calendar field. |
---|---|
month | the value used to set the MONTH calendar field.
Month value is 0-based. e.g., 0 for January. |
date | the value used to set the DAY_OF_MONTH calendar field. |
hourOfDay | the value used to set the HOUR_OF_DAY calendar field. |
minute | the value used to set the MINUTE calendar field. |
public void set (int field, int value)
Sets the given calendar field to the given value. The value is not interpreted by this method regardless of the leniency mode.
Parameters
field | the given calendar field. |
---|---|
value | the value to be set for the given calendar field. |
Throws
ArrayIndexOutOfBoundsException | if the specified field is out of range
(field < 0 || field >= FIELD_COUNT ).
in non-lenient mode. |
---|
public final void set (int year, int month, int date)
Sets the values for the calendar fields YEAR
,
MONTH
, and DAY_OF_MONTH
.
Previous values of other calendar fields are retained. If this is not desired,
call clear()
first.
Parameters
year | the value used to set the YEAR calendar field. |
---|---|
month | the value used to set the MONTH calendar field.
Month value is 0-based. e.g., 0 for January. |
date | the value used to set the DAY_OF_MONTH calendar field. |
public void setFirstDayOfWeek (int value)
Sets what the first day of the week is; e.g., SUNDAY
in the U.S.,
MONDAY
in France.
Parameters
value | the given first day of the week. |
---|
public void setLenient (boolean lenient)
Specifies whether or not date/time interpretation is to be lenient. With lenient interpretation, a date such as "February 942, 1996" will be treated as being equivalent to the 941st day after February 1, 1996. With strict (non-lenient) interpretation, such dates will cause an exception to be thrown. The default is lenient.
Parameters
lenient | true if the lenient mode is to be turned
on; false if it is to be turned off. |
---|
public void setMinimalDaysInFirstWeek (int value)
Sets what the minimal days required in the first week of the year are; For example, if the first week is defined as one that contains the first day of the first month of a year, call this method with value 1. If it must be a full week, use value 7.
Parameters
value | the given minimal days required in the first week of the year. |
---|
See Also
public final void setTime (Date date)
Sets this Calendar's time with the given Date
.
Note: Calling setTime()
with
Date(Long.MAX_VALUE)
or Date(Long.MIN_VALUE)
may yield incorrect field values from get()
.
Parameters
date | the given Date. |
---|
See Also
public void setTimeInMillis (long millis)
Sets this Calendar's current time from the given long value.
Parameters
millis | the new time in UTC milliseconds from the epoch. |
---|
See Also
public void setTimeZone (TimeZone value)
Sets the time zone with the given time zone value.
Parameters
value | the given time zone. |
---|
public void setWeekDate (int weekYear, int weekOfYear, int dayOfWeek)
Sets the date of this Calendar
with the the given date
specifiers - week year, week of year, and day of week.
Unlike the set
method, all of the calendar fields
and time
values are calculated upon return.
If weekOfYear
is out of the valid week-of-year range
in weekYear
, the weekYear
and weekOfYear
values are adjusted in lenient mode, or an IllegalArgumentException
is thrown in non-lenient mode.
The default implementation of this method throws an
UnsupportedOperationException
.
Parameters
weekYear | the week year |
---|---|
weekOfYear | the week number based on weekYear |
dayOfWeek | the day of week value: one of the constants
for the DAY_OF_WEEK field: SUNDAY , ..., SATURDAY . |
Throws
IllegalArgumentException | if any of the given date specifiers is invalid or any of the calendar fields are inconsistent with the given date specifiers in non-lenient mode |
---|---|
UnsupportedOperationException | if any week year numbering isn't supported in this
Calendar . |
public String toString ()
Return a string representation of this calendar. This method
is intended to be used only for debugging purposes, and the
format of the returned string may vary between implementations.
The returned string may be empty but may not be null
.
Returns
- a string representation of this calendar.
Protected Methods
protected void complete ()
Fills in any unset fields in the calendar fields. First, the computeTime()
method is called if the time value (millisecond offset
from the Epoch) has not been calculated from
calendar field values. Then, the computeFields()
method is
called to calculate all calendar field values.
protected abstract void computeFields ()
Converts the current millisecond time value time
to calendar field values in fields[]
.
This allows you to sync up the calendar field values with
a new time that is set for the calendar. The time is not
recomputed first; to recompute the time, then the fields, call the
complete()
method.
See Also
protected abstract void computeTime ()
See Also
protected final int internalGet (int field)
Returns the value of the given calendar field. This method does not involve normalization or validation of the field value.
Parameters
field | the given calendar field. |
---|
Returns
- the value for the given calendar field.