Java(TM) 2 Platform, Standard Edition, v1.2.2 API Specification: Class Calendar - JDK 5 Documentation v1.2.2, Java 2 SDK 英文文档

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java.util
Class Calendar

java.lang.Object
  |
  +--java.util.Calendar

Direct Known Subclasses:: GregorianCalendar

public abstract class Calendar
extends Object
implements Serializable, Cloneable

Calendar is an abstract base class for converting between a Date object and a set of integer fields such as YEAR, MONTH, DAY, HOUR, and so on. (A Date object represents a specific instant in time with millisecond precision. See Date for information about the Date class.)

Subclasses of Calendar interpret a Date according to the rules of a specific calendar system. The JDK provides one concrete subclass of Calendar: GregorianCalendar. Future subclasses could represent the various types of lunar calendars in use in many parts of the world.

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 GregorianCalendar object whose time fields have been initialized with the current date and time:

 Calendar rightNow = Calendar.getInstance();

A Calendar object can produce all the time field values needed to implement the date-time formatting for a particular language and calendar style (for example, Japanese-Gregorian, Japanese-Traditional).

When computing a Date from time fields, two special circumstances may arise: there may be insufficient information to compute the Date (such as only year and month but no day in the month), or there may be inconsistent information (such as "Tuesday, July 15, 1996" -- July 15, 1996 is actually a Monday).

Insufficient information. The calendar will use default information to specify the missing fields. This may vary by calendar; for the Gregorian calendar, the default for a field is the same as that of the start of the epoch: i.e., YEAR = 1970, MONTH = JANUARY, DATE = 1, etc.

Inconsistent information. If fields conflict, the calendar will give preference to fields set more recently. For example, when determining the day, the calendar will look for one of the following combinations of fields. The most recent combination, as determined by the most recently set single field, will be used.

 MONTH + DAY_OF_MONTH
 MONTH + WEEK_OF_MONTH + DAY_OF_WEEK
 MONTH + DAY_OF_WEEK_IN_MONTH + DAY_OF_WEEK
 DAY_OF_YEAR
 DAY_OF_WEEK + WEEK_OF_YEAR

For the time of day:

 HOUR_OF_DAY
 AM_PM + HOUR

Note: for some non-Gregorian calendars, different fields may be necessary for complete disambiguation. For example, a full specification of the historial Arabic astronomical calendar requires year, month, day-of-month and day-of-week in some cases.

Note: There are certain possible ambiguities in interpretation of certain singular times, which are resolved in the following ways:

24:00:00 "belongs" to the following day. That is, 23:59 on Dec 31, 1969 < 24:00 on Jan 1, 1970 < 24:01:00 on Jan 1, 1970
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 methods

Calendar fields can be changed using three methods: set(), add(), and roll().

set(f, value) changes field f to value. In addition, it sets an internal member variable to indicate that field f has been changed. Although field f is changed immediately, the calendar's milliseconds is not recomputed until the next call to get(), getTime(), or getTimeInMillis() is made. Thus, multiple calls to set() do not trigger multiple, unnecessary computations. As a result of changing a field using set(), other fields may also change, depending on the field, the field value, and the calendar system. In addition, get(f) will not necessarily return value after the 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 calendar 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 calendar 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 field f before the call is delta, modulo any overflow that has occurred in field f. 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, 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 than DAY_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 than HOUR.

Example: Consider a GregorianCalendar originally set to August 31, 1999. Calling roll(Calendar.MONTH, 8) sets the calendar to April 30, 1999. Add rule 1 sets the MONTH field to April. Using a GregorianCalendar, the DAY_OF_MONTH cannot be 31 in the month April. Add rule 2 sets it to the closest possible value, 30. Finally, the roll rule maintains the YEAR field value of 1999.

Example: Consider a GregorianCalendar originally set to Sunday June 6, 1999. Calling roll(Calendar.WEEK_OF_MONTH, -1) sets the calendar to Tuesday June 1, 1999, whereas calling add(Calendar.WEEK_OF_MONTH, -1) sets the calendar to Sunday May 30, 1999. This is because the roll rule imposes an additional constraint: The MONTH must not change when the WEEK_OF_MONTH is rolled. Taken together with add rule 1, the resultant date must be between Tuesday June 1 and Saturday June 5. According to add rule 2, the DAY_OF_WEEK, an invariant when changing the WEEK_OF_MONTH, is set to Tuesday, the closest possible value to Sunday (where Sunday is the first day of the week).

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.

See Also:: Date, GregorianCalendar, TimeZone, DateFormat, Serialized Form

Field Summary

static int AM
          Value of the AM_PM field indicating the period of the day from midnight to just before noon.

static int AM_PM
          Field number for get and set indicating whether the HOUR is before or after noon.

static int APRIL
          Value of the MONTH field indicating the fourth month of the year.

protected boolean areFieldsSet
          True if fields[] are in sync with the currently set time.

static int AUGUST
          Value of the MONTH field indicating the eighth month of the year.

static int DATE
          Field number for get and set indicating the day of the month.

static int DAY_OF_MONTH
          Field number for get and set indicating the day of the month.

static int DAY_OF_WEEK
          Field number for get and set indicating the day of the week.

static 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.

static int DAY_OF_YEAR
          Field number for get and set indicating the day number within the current year.

static int DECEMBER
          Value of the MONTH field indicating the twelfth month of the year.

static int DST_OFFSET
          Field number for get and set indicating the daylight savings offset in milliseconds.

static int ERA
          Field number for get and set indicating the era, e.g., AD or BC in the Julian calendar.

static int FEBRUARY
          Value of the MONTH field indicating the second month of the year.

static int FIELD_COUNT
          The number of distict fields recognized by get and set.

protected int[] fields
          The field values for the currently set time for this calendar.

static int FRIDAY
          Value of the DAY_OF_WEEK field indicating Friday.

static int HOUR
          Field number for get and set indicating the hour of the morning or afternoon.

static int HOUR_OF_DAY
          Field number for get and set indicating the hour of the day.

protected boolean[] isSet
          The flags which tell if a specified time field for the calendar is set.

protected boolean isTimeSet
          True if then the value of time is valid.

static int JANUARY
          Value of the MONTH field indicating the first month of the year.

static int JULY
          Value of the MONTH field indicating the seventh month of the year.

static int JUNE
          Value of the MONTH field indicating the sixth month of the year.

static int MARCH
          Value of the MONTH field indicating the third month of the year.

static int MAY
          Value of the MONTH field indicating the fifth month of the year.

static int MILLISECOND
          Field number for get and set indicating the millisecond within the second.

static int MINUTE
          Field number for get and set indicating the minute within the hour.

static int MONDAY
          Value of the DAY_OF_WEEK field indicating Monday.

static int MONTH
          Field number for get and set indicating the month.

static int NOVEMBER
          Value of the MONTH field indicating the eleventh month of the year.

static int OCTOBER
          Value of the MONTH field indicating the tenth month of the year.

static int PM
          Value of the AM_PM field indicating the period of the day from noon to just before midnight.

static int SATURDAY
          Value of the DAY_OF_WEEK field indicating Saturday.

static int SECOND
          Field number for get and set indicating the second within the minute.

static int SEPTEMBER
          Value of the MONTH field indicating the ninth month of the year.

static int SUNDAY
          Value of the DAY_OF_WEEK field indicating Sunday.

static int THURSDAY
          Value of the DAY_OF_WEEK field indicating Thursday.

protected long time
          The currently set time for this calendar, expressed in milliseconds after January 1, 1970, 0:00:00 GMT.

static int TUESDAY
          Value of the DAY_OF_WEEK field indicating Tuesday.

static int UNDECIMBER
          Value of the MONTH field indicating the thirteenth month of the year.

static int WEDNESDAY
          Value of the DAY_OF_WEEK field indicating Wednesday.

static int WEEK_OF_MONTH
          Field number for get and set indicating the week number within the current month.

static int WEEK_OF_YEAR
          Field number for get and set indicating the week number within the current year.

static int YEAR
          Field number for get and set indicating the year.

static int ZONE_OFFSET
          Field number for get and set indicating the raw offset from GMT in milliseconds.

Constructor Summary

protected Calendar()
          Constructs a Calendar with the default time zone and locale.

protected Calendar(TimeZone zone, Locale aLocale)
          Constructs a calendar with the specified time zone and locale.

Method Summary

abstract void add(int field, int amount)
          Date Arithmetic function.

boolean after(Object when)
          Compares the time field records.

boolean before(Object when)
          Compares the time field records.

void clear()
          Clears the values of all the time fields.

void clear(int field)
          Clears the value in the given time field.

Object clone()
          Overrides Cloneable

protected void complete()
          Fills in any unset fields in the time field list.

protected abstract void computeFields()
          Converts the current millisecond time value time to field values in fields[].

protected abstract void computeTime()
          Converts the current field values in fields[] to the millisecond time value time.

boolean equals(Object obj)
          Compares this calendar to the specified object.

int get(int field)
          Gets the value for a given time field.

int getActualMaximum(int field)
          Return the maximum value that this field could have, given the current date.

int getActualMinimum(int field)
          Return the minimum value that this field could have, given the current date.

static Locale[] getAvailableLocales()
          Gets the list of locales for which Calendars are installed.

int getFirstDayOfWeek()
          Gets what the first day of the week is; e.g., Sunday in US, Monday in France.

abstract int getGreatestMinimum(int field)
          Gets the highest minimum value for the given field if varies.

static Calendar getInstance()
          Gets a calendar using the default time zone and locale.

static Calendar getInstance(Locale aLocale)
          Gets a calendar using the default time zone and specified locale.

static Calendar getInstance(TimeZone zone)
          Gets a calendar using the specified time zone and default locale.

static Calendar getInstance(TimeZone zone, Locale aLocale)
          Gets a calendar with the specified time zone and locale.

abstract int getLeastMaximum(int field)
          Gets the lowest maximum value for the given field if varies.

abstract int getMaximum(int field)
          Gets the maximum value for the given time field.

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, getMinimalDaysInFirstWeek returns 1.

abstract int getMinimum(int field)
          Gets the minimum value for the given time field.

Date getTime()
          Gets this Calendar's current time.

protected long getTimeInMillis()
          Gets this Calendar's current time as a long.

TimeZone getTimeZone()
          Gets the time zone.

int hashCode()
          Returns a hash code for this calendar.

protected int internalGet(int field)
          Gets the value for a given time field.

boolean isLenient()
          Tell whether date/time interpretation is to be lenient.

boolean isSet(int field)
          Determines if the given time field has a value set.

abstract void roll(int field, boolean up)
          Time Field Rolling function.

void roll(int field, int amount)
          Time Field Rolling function.

void set(int field, int value)
          Sets the time field with the given value.

void set(int year, int month, int date)
          Sets the values for the fields year, month, and date.

void set(int year, int month, int date, int hour, int minute)
          Sets the values for the fields year, month, date, hour, and minute.

void set(int year, int month, int date, int hour, int minute, int second)
          Sets the values for the fields year, month, date, hour, minute, and second.

void setFirstDayOfWeek(int value)
          Sets what the first day of the week is; e.g., Sunday in US, Monday in France.

void setLenient(boolean lenient)
          Specify 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 the method with value 1.

void setTime(Date date)
          Sets this Calendar's current time with the given Date.

protected void setTimeInMillis(long millis)
          Sets this Calendar's current time from the given long value.

void setTimeZone(TimeZone value)
          Sets the time zone with the given time zone value.

String toString()
          Return a string representation of this calendar.

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

ERA

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 Also:: GregorianCalendar.AD, GregorianCalendar.BC

YEAR

public static final int YEAR

Field number for get and set indicating the year. This is a calendar-specific value.

MONTH

public static final int MONTH

Field number for get and set indicating the month. This is a calendar-specific value.

WEEK_OF_YEAR

public static final int WEEK_OF_YEAR

Field number for get and set indicating the week number within the current year.

WEEK_OF_MONTH

public static final int WEEK_OF_MONTH

Field number for get and set indicating the week number within the current month.

DATE

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.

See Also:: DAY_OF_MONTH

DAY_OF_MONTH

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.

See Also:: DATE

DAY_OF_YEAR

public static final int DAY_OF_YEAR

Field number for get and set indicating the day number within the current year.

DAY_OF_WEEK

public static final int DAY_OF_WEEK

Field number for get and set indicating the day of the week.

DAY_OF_WEEK_IN_MONTH

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. Example: the last Sunday in October is specified as DAY_OF_WEEK = Sunday, DAY_OF_WEEK_IN_MONTH = -1.

See Also:: DAY_OF_WEEK

AM_PM

public 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.

See Also:: AM, PM, HOUR

HOUR

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. E.g., at 10:04:15.250 PM the HOUR is 10.

See Also:: AM_PM, HOUR_OF_DAY

HOUR_OF_DAY

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:: HOUR

MINUTE

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.

SECOND

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.

MILLISECOND

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.

ZONE_OFFSET

public static final int ZONE_OFFSET

Field number for get and set indicating the raw offset from GMT in milliseconds.

DST_OFFSET

public static final int DST_OFFSET

Field number for get and set indicating the daylight savings offset in milliseconds.

FIELD_COUNT

public static final int FIELD_COUNT

The number of distict fields recognized by get and set. Field numbers range from 0..FIELD_COUNT-1.

SUNDAY

public static final int SUNDAY

Value of the DAY_OF_WEEK field indicating Sunday.

MONDAY

public static final int MONDAY

Value of the DAY_OF_WEEK field indicating Monday.

TUESDAY

public static final int TUESDAY

Value of the DAY_OF_WEEK field indicating Tuesday.

WEDNESDAY

public static final int WEDNESDAY

Value of the DAY_OF_WEEK field indicating Wednesday.

THURSDAY

public static final int THURSDAY

Value of the DAY_OF_WEEK field indicating Thursday.

FRIDAY

public static final int FRIDAY

Value of the DAY_OF_WEEK field indicating Friday.

SATURDAY

public static final int SATURDAY

Value of the DAY_OF_WEEK field indicating Saturday.

JANUARY

public static final int JANUARY

Value of the MONTH field indicating the first month of the year.

FEBRUARY

public static final int FEBRUARY

Value of the MONTH field indicating the second month of the year.

MARCH

public static final int MARCH

Value of the MONTH field indicating the third month of the year.

APRIL

public static final int APRIL

Value of the MONTH field indicating the fourth month of the year.

MAY

public static final int MAY

Value of the MONTH field indicating the fifth month of the year.

JUNE

public static final int JUNE

Value of the MONTH field indicating the sixth month of the year.

JULY

public static final int JULY

Value of the MONTH field indicating the seventh month of the year.

AUGUST

public static final int AUGUST

Value of the MONTH field indicating the eighth month of the year.

SEPTEMBER

public static final int SEPTEMBER

Value of the MONTH field indicating the ninth month of the year.

OCTOBER

public static final int OCTOBER

Value of the MONTH field indicating the tenth month of the year.

NOVEMBER

public static final int NOVEMBER

Value of the MONTH field indicating the eleventh month of the year.

DECEMBER

public static final int DECEMBER

Value of the MONTH field indicating the twelfth month of the year.

UNDECIMBER

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.

AM

public static final int AM

Value of the AM_PM field indicating the period of the day from midnight to just before noon.

PM

public static final int PM

Value of the AM_PM field indicating the period of the day from noon to just before midnight.

fields

protected int[] fields

The 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.

isSet

protected boolean[] isSet

The flags which tell if a specified time 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.

time

protected long time

The currently set time for this calendar, expressed in milliseconds after January 1, 1970, 0:00:00 GMT.

See Also:: isTimeSet

isTimeSet

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:: time

areFieldsSet

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.

Constructor Detail

Calendar

protected Calendar()

Constructs a Calendar with the default time zone and locale.

See Also:: TimeZone.getDefault()

Calendar

protected Calendar(TimeZone zone,
                   Locale aLocale)

Constructs a calendar with the specified time zone and locale.

Parameters:: zone - the time zone to use; aLocale - the locale for the week data

Method Detail

getInstance

public static Calendar getInstance()

Gets a calendar using the default time zone and locale.

Returns:: a Calendar.

getInstance

public static Calendar getInstance(TimeZone zone)

Gets a calendar using the specified time zone and default locale.

Parameters:: zone - the time zone to use
Returns:: a Calendar.

getInstance

public static Calendar getInstance(Locale aLocale)

Gets a calendar using the default time zone and specified locale.

Parameters:: aLocale - the locale for the week data
Returns:: a Calendar.

getInstance

public static Calendar getInstance(TimeZone zone,
                                   Locale aLocale)

Gets a calendar with the specified time zone and locale.

Parameters:: zone - the time zone to use; aLocale - the locale for the week data
Returns:: a Calendar.

getAvailableLocales

public static Locale[] getAvailableLocales()

Gets the list of locales for which Calendars are installed.

Returns:: the list of locales for which Calendars are installed.

computeTime

protected abstract void computeTime()

Converts the current field values in fields[] to the millisecond time value time.

computeFields

protected abstract void computeFields()

Converts the current millisecond time value time to field values in fields[]. This allows you to sync up the time 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:: complete()

getTime

public final Date getTime()

Gets this Calendar's current time.

Returns:: the current time.

setTime

public final void setTime(Date date)

Sets this Calendar's current 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.

getTimeInMillis

protected long getTimeInMillis()

Gets this Calendar's current time as a long.

Returns:: the current time as UTC milliseconds from the epoch.

setTimeInMillis

protected void setTimeInMillis(long millis)

Sets this Calendar's current time from the given long value.

Parameters:: date - the new time in UTC milliseconds from the epoch.

get

public final int get(int field)

Gets the value for a given time field.

Parameters:: field - the given time field.
Returns:: the value for the given time field.

internalGet

protected final int internalGet(int field)

Gets the value for a given time field. This is an internal fast time field value getter for the subclasses.

Parameters:: field - the given time field.
Returns:: the value for the given time field.

set

public final void set(int field,
                      int value)

Sets the time field with the given value.

Parameters:: field - the given time field.; value - the value to be set for the given time field.

set

public final void set(int year,
                      int month,
                      int date)

Sets the values for the fields year, month, and date. Previous values of other fields are retained. If this is not desired, call clear first.

Parameters:: year - the value used to set the YEAR time field.; month - the value used to set the MONTH time field. Month value is 0-based. e.g., 0 for January.; date - the value used to set the DATE time field.

set

public final void set(int year,
                      int month,
                      int date,
                      int hour,
                      int minute)

Sets the values for the fields year, month, date, hour, 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 time field.; month - the value used to set the MONTH time field. Month value is 0-based. e.g., 0 for January.; date - the value used to set the DATE time field.; hour - the value used to set the HOUR_OF_DAY time field.; minute - the value used to set the MINUTE time field.

set

public final void set(int year,
                      int month,
                      int date,
                      int hour,
                      int minute,
                      int second)

Sets the values for the fields year, month, date, hour, 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 time field.; month - the value used to set the MONTH time field. Month value is 0-based. e.g., 0 for January.; date - the value used to set the DATE time field.; hour - the value used to set the HOUR_OF_DAY time field.; minute - the value used to set the MINUTE time field.; second - the value used to set the SECOND time field.

clear

public final void clear()

Clears the values of all the time fields.

clear

public final void clear(int field)

Clears the value in the given time field.

Parameters:: field - the time field to be cleared.

isSet

public final boolean isSet(int field)

Determines if the given time field has a value set.

Returns:: true if the given time field has a value set; false otherwise.

complete

protected void complete()

Fills in any unset fields in the time field list.

equals

public boolean equals(Object obj)

Compares this calendar to the specified object. The result is true if and only if the argument is not null and is a Calendar object that represents the same calendar as this object.

Overrides:: equals in class Object

Parameters:: obj - the object to compare with.
Returns:: true if the objects are the same; false otherwise.

hashCode

public int hashCode()

Returns a hash code for this calendar.

Overrides:: hashCode in class Object

Returns:: a hash code value for this object.

before

public boolean before(Object when)

Compares the time field records. Equivalent to comparing result of conversion to UTC.

Parameters:: when - the Calendar to be compared with this Calendar.
Returns:: true if the current time of this Calendar is before the time of Calendar when; false otherwise.

after

public boolean after(Object when)

Compares the time field records. Equivalent to comparing result of conversion to UTC.

Parameters:: when - the Calendar to be compared with this Calendar.
Returns:: true if the current time of this Calendar is after the time of Calendar when; false otherwise.

add

public abstract void add(int field,
                         int amount)

Date Arithmetic function. Adds the specified (signed) amount of time to the given time 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.DATE, -5).

Parameters:: field - the time field.; amount - the amount of date or time to be added to the field.

roll

public abstract void roll(int field,
                          boolean up)

Time Field Rolling function. Rolls (up/down) a single unit of time on the given time field. 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.

roll

public void roll(int field,
                 int amount)

Time Field Rolling function. Rolls up or down the specified number of units on the given time field. (A negative roll amount means to roll down.) [NOTE: This default implementation on Calendar just repeatedly calls the version of roll() that takes a boolean and 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.

setTimeZone

public void setTimeZone(TimeZone value)

Sets the time zone with the given time zone value.

Parameters:: value - the given time zone.

getTimeZone

public TimeZone getTimeZone()

Gets the time zone.

Returns:: the time zone object associated with this calendar.

setLenient

public void setLenient(boolean lenient)

Specify 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 interpretation, such dates will cause an exception to be thrown.

See Also:: DateFormat.setLenient(boolean)

isLenient

public boolean isLenient()

Tell whether date/time interpretation is to be lenient.

setFirstDayOfWeek

public void setFirstDayOfWeek(int value)

Sets what the first day of the week is; e.g., Sunday in US, Monday in France.

Parameters:: value - the given first day of the week.

getFirstDayOfWeek

public int getFirstDayOfWeek()

Gets what the first day of the week is; e.g., Sunday in US, Monday in France.

Returns:: the first day of the week.

setMinimalDaysInFirstWeek

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 the 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.

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, getMinimalDaysInFirstWeek returns 1. If the minimal days required must be a full week, getMinimalDaysInFirstWeek returns 7.

Returns:: the minimal days required in the first week of the year.

getMinimum

public abstract int getMinimum(int field)

Gets the minimum value for the given time field. e.g., for Gregorian DAY_OF_MONTH, 1.

Parameters:: field - the given time field.
Returns:: the minimum value for the given time field.

getMaximum

public abstract int getMaximum(int field)

Gets the maximum value for the given time field. e.g. for Gregorian DAY_OF_MONTH, 31.

Parameters:: field - the given time field.
Returns:: the maximum value for the given time field.

getGreatestMinimum

public abstract int getGreatestMinimum(int field)

Gets the highest minimum value for the given field if varies. Otherwise same as getMinimum(). For Gregorian, no difference.

Parameters:: field - the given time field.
Returns:: the highest minimum value for the given time field.

getLeastMaximum

public abstract int getLeastMaximum(int field)

Gets the lowest maximum value for the given field if varies. Otherwise same as getMaximum(). e.g., for Gregorian DAY_OF_MONTH, 28.

Parameters:: field - the given time field.
Returns:: the lowest maximum value for the given time field.

getActualMinimum

public int getActualMinimum(int field)

Return the minimum value that this field could have, given the current date. For the Gregorian calendar, this is the same as getMinimum() and getGreatestMinimum(). The version of this function on Calendar uses an iterative algorithm to determine the actual minimum value for the field. There is almost always a more efficient way to accomplish this (in most cases, you can simply return getMinimum()). GregorianCalendar overrides this function with a more efficient implementation.

Parameters:: field - the field to determine the minimum of
Returns:: the minimum of the given field for the current date of this Calendar

getActualMaximum

public int getActualMaximum(int field)

Return the maximum value that this field could have, given the current date. For example, with the date "Feb 3, 1997" and the DAY_OF_MONTH field, the actual maximum would be 28; for "Feb 3, 1996" it s 29. Similarly for a Hebrew calendar, for some years the actual maximum for MONTH is 12, and for others 13. The version of this function on Calendar uses an iterative algorithm to determine the actual maximum value for the field. There is almost always a more efficient way to accomplish this (in most cases, you can simply return getMaximum()). GregorianCalendar overrides this function with a more efficient implementation.

Parameters:: field - the field to determine the maximum of
Returns:: the maximum of the given field for the current date of this Calendar

clone

public Object clone()

Overrides Cloneable

Overrides:: clone in class Object

Tags copied from class: Object

Returns:: a clone of this instance.
Throws:: CloneNotSupportedException - if the object's class does not support the Cloneable interface. Subclasses that override the clone method can also throw this exception to indicate that an instance cannot be cloned.; OutOfMemoryError - if there is not enough memory.
See Also:: Cloneable

toString

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.

Overrides:: toString in class Object

Returns:: a string representation of this calendar.

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Field Summary
`static int`	`AM` Value of the `AM_PM` field indicating the period of the day from midnight to just before noon.
`static int`	`AM_PM` Field number for `get` and `set` indicating whether the `HOUR` is before or after noon.
`static int`	`APRIL` Value of the `MONTH` field indicating the fourth month of the year.
`protected boolean`	`areFieldsSet` True if `fields[]` are in sync with the currently set time.
`static int`	`AUGUST` Value of the `MONTH` field indicating the eighth month of the year.
`static int`	`DATE` Field number for `get` and `set` indicating the day of the month.
`static int`	`DAY_OF_MONTH` Field number for `get` and `set` indicating the day of the month.
`static int`	`DAY_OF_WEEK` Field number for `get` and `set` indicating the day of the week.
`static 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.
`static int`	`DAY_OF_YEAR` Field number for `get` and `set` indicating the day number within the current year.
`static int`	`DECEMBER` Value of the `MONTH` field indicating the twelfth month of the year.
`static int`	`DST_OFFSET` Field number for `get` and `set` indicating the daylight savings offset in milliseconds.
`static int`	`ERA` Field number for `get` and `set` indicating the era, e.g., AD or BC in the Julian calendar.
`static int`	`FEBRUARY` Value of the `MONTH` field indicating the second month of the year.
`static int`	`FIELD_COUNT` The number of distict fields recognized by `get` and `set`.
`protected int[]`	`fields` The field values for the currently set time for this calendar.
`static int`	`FRIDAY` Value of the `DAY_OF_WEEK` field indicating Friday.
`static int`	`HOUR` Field number for `get` and `set` indicating the hour of the morning or afternoon.
`static int`	`HOUR_OF_DAY` Field number for `get` and `set` indicating the hour of the day.
`protected boolean[]`	`isSet` The flags which tell if a specified time field for the calendar is set.
`protected boolean`	`isTimeSet` True if then the value of `time` is valid.
`static int`	`JANUARY` Value of the `MONTH` field indicating the first month of the year.
`static int`	`JULY` Value of the `MONTH` field indicating the seventh month of the year.
`static int`	`JUNE` Value of the `MONTH` field indicating the sixth month of the year.
`static int`	`MARCH` Value of the `MONTH` field indicating the third month of the year.
`static int`	`MAY` Value of the `MONTH` field indicating the fifth month of the year.
`static int`	`MILLISECOND` Field number for `get` and `set` indicating the millisecond within the second.
`static int`	`MINUTE` Field number for `get` and `set` indicating the minute within the hour.
`static int`	`MONDAY` Value of the `DAY_OF_WEEK` field indicating Monday.
`static int`	`MONTH` Field number for `get` and `set` indicating the month.
`static int`	`NOVEMBER` Value of the `MONTH` field indicating the eleventh month of the year.
`static int`	`OCTOBER` Value of the `MONTH` field indicating the tenth month of the year.
`static int`	`PM` Value of the `AM_PM` field indicating the period of the day from noon to just before midnight.
`static int`	`SATURDAY` Value of the `DAY_OF_WEEK` field indicating Saturday.
`static int`	`SECOND` Field number for `get` and `set` indicating the second within the minute.
`static int`	`SEPTEMBER` Value of the `MONTH` field indicating the ninth month of the year.
`static int`	`SUNDAY` Value of the `DAY_OF_WEEK` field indicating Sunday.
`static int`	`THURSDAY` Value of the `DAY_OF_WEEK` field indicating Thursday.
`protected long`	`time` The currently set time for this calendar, expressed in milliseconds after January 1, 1970, 0:00:00 GMT.
`static int`	`TUESDAY` Value of the `DAY_OF_WEEK` field indicating Tuesday.
`static int`	`UNDECIMBER` Value of the `MONTH` field indicating the thirteenth month of the year.
`static int`	`WEDNESDAY` Value of the `DAY_OF_WEEK` field indicating Wednesday.
`static int`	`WEEK_OF_MONTH` Field number for `get` and `set` indicating the week number within the current month.
`static int`	`WEEK_OF_YEAR` Field number for `get` and `set` indicating the week number within the current year.
`static int`	`YEAR` Field number for `get` and `set` indicating the year.
`static int`	`ZONE_OFFSET` Field number for `get` and `set` indicating the raw offset from GMT in milliseconds.

Constructor Summary
`protected`	`Calendar()` Constructs a Calendar with the default time zone and locale.
`protected`	`Calendar(TimeZone zone, Locale aLocale)` Constructs a calendar with the specified time zone and locale.

Method Summary
`abstract void`	`add(int field, int amount)` Date Arithmetic function.
`boolean`	`after(Object when)` Compares the time field records.
`boolean`	`before(Object when)` Compares the time field records.
`void`	`clear()` Clears the values of all the time fields.
`void`	`clear(int field)` Clears the value in the given time field.
`Object`	`clone()` Overrides Cloneable
`protected void`	`complete()` Fills in any unset fields in the time field list.
`protected abstract void`	`computeFields()` Converts the current millisecond time value `time` to field values in `fields[]`.
`protected abstract void`	`computeTime()` Converts the current field values in `fields[]` to the millisecond time value `time`.
`boolean`	`equals(Object obj)` Compares this calendar to the specified object.
`int`	`get(int field)` Gets the value for a given time field.
`int`	`getActualMaximum(int field)` Return the maximum value that this field could have, given the current date.
`int`	`getActualMinimum(int field)` Return the minimum value that this field could have, given the current date.
`static Locale[]`	`getAvailableLocales()` Gets the list of locales for which Calendars are installed.
`int`	`getFirstDayOfWeek()` Gets what the first day of the week is; e.g., Sunday in US, Monday in France.
`abstract int`	`getGreatestMinimum(int field)` Gets the highest minimum value for the given field if varies.
`static Calendar`	`getInstance()` Gets a calendar using the default time zone and locale.
`static Calendar`	`getInstance(Locale aLocale)` Gets a calendar using the default time zone and specified locale.
`static Calendar`	`getInstance(TimeZone zone)` Gets a calendar using the specified time zone and default locale.
`static Calendar`	`getInstance(TimeZone zone, Locale aLocale)` Gets a calendar with the specified time zone and locale.
`abstract int`	`getLeastMaximum(int field)` Gets the lowest maximum value for the given field if varies.
`abstract int`	`getMaximum(int field)` Gets the maximum value for the given time field.
`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, getMinimalDaysInFirstWeek returns 1.
`abstract int`	`getMinimum(int field)` Gets the minimum value for the given time field.
`Date`	`getTime()` Gets this Calendar's current time.
`protected long`	`getTimeInMillis()` Gets this Calendar's current time as a long.
`TimeZone`	`getTimeZone()` Gets the time zone.
`int`	`hashCode()` Returns a hash code for this calendar.
`protected int`	`internalGet(int field)` Gets the value for a given time field.
`boolean`	`isLenient()` Tell whether date/time interpretation is to be lenient.
`boolean`	`isSet(int field)` Determines if the given time field has a value set.
`abstract void`	`roll(int field, boolean up)` Time Field Rolling function.
`void`	`roll(int field, int amount)` Time Field Rolling function.
`void`	`set(int field, int value)` Sets the time field with the given value.
`void`	`set(int year, int month, int date)` Sets the values for the fields year, month, and date.
`void`	`set(int year, int month, int date, int hour, int minute)` Sets the values for the fields year, month, date, hour, and minute.
`void`	`set(int year, int month, int date, int hour, int minute, int second)` Sets the values for the fields year, month, date, hour, minute, and second.
`void`	`setFirstDayOfWeek(int value)` Sets what the first day of the week is; e.g., Sunday in US, Monday in France.
`void`	`setLenient(boolean lenient)` Specify 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 the method with value 1.
`void`	`setTime(Date date)` Sets this Calendar's current time with the given Date.
`protected void`	`setTimeInMillis(long millis)` Sets this Calendar's current time from the given long value.
`void`	`setTimeZone(TimeZone value)` Sets the time zone with the given time zone value.
`String`	`toString()` Return a string representation of this calendar.

Java(TM) 2 Platform, Standard Edition, v1.2.2 API Specification: Class Calendar - JDK 5 Documentation v1.2.2, Java 2 SDK 英文文档

java.util Class Calendar

ERA

YEAR

MONTH

WEEK_OF_YEAR

WEEK_OF_MONTH

DATE

DAY_OF_MONTH

DAY_OF_YEAR

DAY_OF_WEEK

DAY_OF_WEEK_IN_MONTH

AM_PM

HOUR

HOUR_OF_DAY

MINUTE

SECOND

MILLISECOND

ZONE_OFFSET

DST_OFFSET

FIELD_COUNT

SUNDAY

MONDAY

TUESDAY

WEDNESDAY

THURSDAY

FRIDAY

SATURDAY

JANUARY

FEBRUARY

MARCH

APRIL

MAY

JUNE

JULY

AUGUST

SEPTEMBER

OCTOBER

NOVEMBER

DECEMBER

UNDECIMBER

AM

PM

fields

isSet

time

isTimeSet

areFieldsSet

Calendar

Calendar

getInstance

getInstance

getInstance

getInstance

getAvailableLocales

computeTime

computeFields

getTime

setTime

getTimeInMillis

setTimeInMillis

get

internalGet

set

set

set

set

clear

clear

isSet

complete

equals

hashCode

before

after

add

roll

roll

setTimeZone

getTimeZone

java.util
Class Calendar