public abstract class Calendar extends Object implements Serializable, Cloneable, Comparable<Calendar>
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.
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.
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.
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 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.
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_YEARFor the time of day fields:
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:
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.
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
fafter the call minus the value of fieldfbefore 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
fis 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.HOURis 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_MONTHis 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.
System.currentTimeMillis(), Date, GregorianCalendar, TimeZone, DateFormat, Serialized Form| Modifier and Type | Class and Description |
|---|---|
static class |
Calendar.Builder
|
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.
GregorianCalendar.AD, GregorianCalendar.BC, Constant Field Valuespublic 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 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.
JANUARY, FEBRUARY, MARCH, APRIL, MAY, JUNE, JULY, AUGUST, SEPTEMBER, OCTOBER, NOVEMBER, DECEMBER, UNDECIMBER, Constant Field Valuespublic 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.
getFirstDayOfWeek(), getMinimalDaysInFirstWeek(), Constant Field Valuespublic 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.
getFirstDayOfWeek(), getMinimalDaysInFirstWeek(), Constant Field Valuespublic 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.
DAY_OF_MONTH, Constant Field Valuespublic 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.
DATE, Constant Field Valuespublic 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 DAY_OF_WEEK
Field number for get and set indicating the day of the week. This field takes values SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, and SATURDAY.
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.
DAY_OF_WEEK, WEEK_OF_MONTH, Constant Field Valuespublic static final int AM_PM
Field number for get and set indicating whether the HOUR is before or after noon. E.g., at 10:04:15.250 PM the AM_PM is PM.
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.
AM_PM, HOUR_OF_DAY, Constant Field Valuespublic 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.
HOUR, Constant Field Valuespublic 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 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 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 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.
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 FIELD_COUNT
The number of distinct fields recognized by get and set. Field numbers range from 0..FIELD_COUNT-1.
public static final int SUNDAY
Value of the DAY_OF_WEEK field indicating Sunday.
public static final int MONDAY
Value of the DAY_OF_WEEK field indicating Monday.
public static final int TUESDAY
Value of the DAY_OF_WEEK field indicating Tuesday.
public static final int WEDNESDAY
Value of the DAY_OF_WEEK field indicating Wednesday.
public static final int THURSDAY
Value of the DAY_OF_WEEK field indicating Thursday.
public static final int FRIDAY
Value of the DAY_OF_WEEK field indicating Friday.
public static final int SATURDAY
Value of the DAY_OF_WEEK field indicating Saturday.
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 FEBRUARY
Value of the MONTH field indicating the second month of the year in the Gregorian and Julian calendars.
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 APRIL
Value of the MONTH field indicating the fourth 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 JUNE
Value of the MONTH field indicating the sixth 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 AUGUST
Value of the MONTH field indicating the eighth month of the year in the Gregorian and Julian calendars.
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 OCTOBER
Value of the MONTH field indicating the tenth month of the year in the Gregorian and Julian calendars.
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 DECEMBER
Value of the MONTH field indicating the twelfth month of the year in the Gregorian and Julian calendars.
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 AM
Value of the AM_PM field indicating the period of the day from midnight to just before noon.
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 ALL_STYLES
A style specifier for getDisplayNames indicating names in all styles, such as "January" and "Jan".
SHORT_FORMAT, LONG_FORMAT, SHORT_STANDALONE, LONG_STANDALONE, SHORT, LONG, Constant Field Valuespublic static final int SHORT
A style specifier for getDisplayName and getDisplayNames equivalent to SHORT_FORMAT.
SHORT_STANDALONE, LONG, Constant Field Valuespublic static final int LONG
A style specifier for getDisplayName and getDisplayNames equivalent to LONG_FORMAT.
LONG_STANDALONE, SHORT, Constant Field Valuespublic 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.
NARROW_STANDALONE, SHORT_FORMAT, LONG_FORMAT, Constant Field Valuespublic 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.
NARROW_FORMAT, SHORT_STANDALONE, LONG_STANDALONE, Constant Field Valuespublic static final int SHORT_FORMAT
A style specifier for getDisplayName and getDisplayNames indicating a short name used for format.
SHORT_STANDALONE, LONG_FORMAT, LONG_STANDALONE, Constant Field Valuespublic static final int LONG_FORMAT
A style specifier for getDisplayName and getDisplayNames indicating a long name used for format.
LONG_STANDALONE, SHORT_FORMAT, SHORT_STANDALONE, Constant Field Valuespublic 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.
SHORT_FORMAT, LONG_FORMAT, LONG_STANDALONE, Constant Field Valuespublic 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.
LONG_FORMAT, SHORT_FORMAT, SHORT_STANDALONE, Constant Field Valuesprotected 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 long time
The currently set time for this calendar, expressed in milliseconds after January 1, 1970, 0:00:00 GMT.
isTimeSetprotected boolean isTimeSet
True if then the value of time is valid. The time is made invalid by a change to an item of field[].
timeprotected 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 Calendar()
Constructs a Calendar with the default time zone and the default FORMAT locale.
TimeZone.getDefault()protected Calendar(TimeZone zone,
Locale aLocale) Constructs a calendar with the specified time zone and locale.
zone - the time zone to useaLocale - the locale for the week datapublic 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.
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.
zone - the time zone to usepublic 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.
aLocale - the locale for the week datapublic 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.
zone - the time zone to useaLocale - the locale for the week datapublic static 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.
Calendar instances are available.protected abstract void computeTime()
Converts the current calendar field values in fields[] to the millisecond time value time.
complete(), computeFields()
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.
computeTime()public final Date getTime()
Returns a Date object representing this Calendar's time value (millisecond offset from the Epoch").
Date representing the time value.setTime(Date), getTimeInMillis()
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().
date - the given Date.getTime(), setTimeInMillis(long)
public long getTimeInMillis()
Returns this Calendar's time value in milliseconds.
getTime(), setTimeInMillis(long)
public void setTimeInMillis(long millis)
Sets this Calendar's current time from the given long value.
millis - the new time in UTC milliseconds from the epoch.setTime(Date), getTimeInMillis()
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.
field - the given calendar field.ArrayIndexOutOfBoundsException - if the specified field is out of range (field < 0 || field >= FIELD_COUNT).set(int,int), complete()
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.
field - the given calendar field.get(int)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.
field - the given calendar field.value - the value to be set for the given calendar field.ArrayIndexOutOfBoundsException - if the specified field is out of range (field < 0 || field >= FIELD_COUNT). in non-lenient mode.set(int,int,int), set(int,int,int,int,int), set(int,int,int,int,int,int), get(int)
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.
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.set(int,int), set(int,int,int,int,int), set(int,int,int,int,int,int)
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.
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.set(int,int), set(int,int,int), set(int,int,int,int,int,int)
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.
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.set(int,int), set(int,int,int), set(int,int,int,int,int)
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.
clear(int)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.
field - the calendar field to be cleared.clear()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.
field - the calendar field to testtrue if the given calendar field has a value set; false otherwise.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.
field - the calendar field for which the string representation is returnedstyle - 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)field in the given style, or null if no string representation is applicable.IllegalArgumentException - if field or style is invalid, or if this Calendar is non-lenient and any of the calendar fields have invalid valuesNullPointerException - if locale is nullpublic 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 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().
field - the calendar field for which the display names are returnedstyle - 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 namesMap containing all display names in style and locale and their field values, or null if no display names are defined for field
IllegalArgumentException - if field or style is invalid, or if this Calendar is non-lenient and any of the calendar fields have invalid valuesNullPointerException - if locale is nullprotected 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.
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".
Set containing all available calendar typesgetCalendarType(), Calendar.Builder.setCalendarType(String), Locale.getUnicodeLocaleType(String)
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.
Calendar instanceLocale.Builder.setLocale(Locale), Locale.Builder.setUnicodeLocaleKeyword(String, String)
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 Calendars, this method returns false.
Use the compareTo method to compare only the time values.
equals in class Object
obj - the object to compare with.true if this object is equal to obj; false otherwise.Object.hashCode(), HashMap
public int hashCode()
Returns a hash code for this calendar.
hashCode in class Object
Object.equals(java.lang.Object), System.identityHashCode(java.lang.Object)
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) < 0if and only if
when is a Calendar instance. Otherwise, the method returns false. when - the Object to be comparedtrue if the time of this Calendar is before the time represented by when; false otherwise.compareTo(Calendar)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) > 0if and only if
when is a Calendar instance. Otherwise, the method returns false. when - the Object to be comparedtrue if the time of this Calendar is after the time represented by when; false otherwise.compareTo(Calendar)public int compareTo(Calendar anotherCalendar)
Compares the time values (millisecond offsets from the Epoch) represented by two Calendar objects.
compareTo in interface Comparable<Calendar>
anotherCalendar - the Calendar to be compared.0 if the time represented by the argument is equal to the time represented by this Calendar; a value less than 0 if the time of this Calendar is before the time represented by the argument; and a value greater than 0 if the time of this Calendar is after the time represented by the argument.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 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).
field - the calendar field.amount - the amount of date or time to be added to the field.roll(int,int), set(int,int)
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.
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.add(int,int), set(int,int)
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.
field - the calendar field.amount - the signed amount to add to the calendar field.roll(int,boolean), add(int,int), set(int,int)
public void setTimeZone(TimeZone value)
Sets the time zone with the given time zone value.
value - the given time zone.public TimeZone getTimeZone()
Gets the time zone.
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.
lenient - true if the lenient mode is to be turned on; false if it is to be turned off.isLenient(), DateFormat.setLenient(boolean)
public boolean isLenient()
Tells whether date/time interpretation is to be lenient.
true if the interpretation mode of this calendar is lenient; false otherwise.setLenient(boolean)public void setFirstDayOfWeek(int value)
Sets what the first day of the week is; e.g., SUNDAY in the U.S., MONDAY in France.
value - the given first day of the week.getFirstDayOfWeek(), getMinimalDaysInFirstWeek()
public int getFirstDayOfWeek()
Gets what the first day of the week is; e.g., SUNDAY in the U.S., MONDAY in France.
setFirstDayOfWeek(int), getMinimalDaysInFirstWeek()
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.
value - the given minimal days required in the first week of the year.getMinimalDaysInFirstWeek()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.
setMinimalDaysInFirstWeek(int)public boolean isWeekDateSupported()
Returns whether this Calendar supports week dates.
The default implementation of this method returns false.
true if this Calendar supports week dates; false otherwise.getWeekYear(), setWeekDate(int,int,int), getWeeksInWeekYear()
public int getWeekYear()
Returns the week year represented by this Calendar. The week year is in sync with the week cycle. The first day of the first week is the first day of the week year.
The default implementation of this method throws an UnsupportedOperationException.
Calendar
UnsupportedOperationException - if any week year numbering isn't supported in this Calendar.isWeekDateSupported(), getFirstDayOfWeek(), getMinimalDaysInFirstWeek()
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.
weekYear - the week yearweekOfYear - the week number based on weekYear
dayOfWeek - the day of week value: one of the constants for the DAY_OF_WEEK field: SUNDAY, ..., SATURDAY.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 modeUnsupportedOperationException - if any week year numbering isn't supported in this Calendar.isWeekDateSupported(), getFirstDayOfWeek(), getMinimalDaysInFirstWeek()
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.
UnsupportedOperationException - if any week year numbering isn't supported in this Calendar.WEEK_OF_YEAR, isWeekDateSupported(), getWeekYear(), getActualMaximum(int)
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.
field - the calendar field.getMaximum(int), getGreatestMinimum(int), getLeastMaximum(int), getActualMinimum(int), getActualMaximum(int)
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.
field - the calendar field.getMinimum(int), getGreatestMinimum(int), getLeastMaximum(int), getActualMinimum(int), getActualMaximum(int)
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.
field - the calendar field.getMinimum(int), getMaximum(int), getLeastMaximum(int), getActualMinimum(int), getActualMaximum(int)
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.
field - the calendar field.getMinimum(int), getMaximum(int), getGreatestMinimum(int), getActualMinimum(int), getActualMaximum(int)
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().
field - the calendar fieldCalendar
getMinimum(int), getMaximum(int), getGreatestMinimum(int), getLeastMaximum(int), getActualMaximum(int)
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.
field - the calendar fieldCalendar
getMinimum(int), getMaximum(int), getGreatestMinimum(int), getLeastMaximum(int), getActualMinimum(int)
public Object clone()
Creates and returns a copy of this object.
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.
public final Instant toInstant()
Converts this object to an Instant.
The conversion creates an Instant that represents the same point on the time-line as this Calendar.
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