* {@code Month} is an enum representing the 12 months of the year - * January, February, March, April, May, June, July, August, September, October, * November and December. *
* In addition to the textual enum name, each month-of-year has an {@code int} value. * The {@code int} value follows normal usage and the ISO-8601 standard, * from 1 (January) to 12 (December). It is recommended that applications use the enum * rather than the {@code int} value to ensure code clarity. *
* Do not use {@code ordinal()} to obtain the numeric representation of {@code Month}. * Use {@code getValue()} instead. *
* This enum represents a common concept that is found in many calendar systems. * As such, this enum may be used by any calendar system that has the month-of-year * concept defined exactly equivalent to the ISO-8601 calendar system. * * @implSpec * This is an immutable and thread-safe enum. * * @since 1.8 */ public enum Month implements TemporalAccessor, TemporalAdjuster { /** * The singleton instance for the month of January with 31 days. * This has the numeric value of {@code 1}. */ JANUARY, /** * The singleton instance for the month of February with 28 days, or 29 in a leap year. * This has the numeric value of {@code 2}. */ FEBRUARY, /** * The singleton instance for the month of March with 31 days. * This has the numeric value of {@code 3}. */ MARCH, /** * The singleton instance for the month of April with 30 days. * This has the numeric value of {@code 4}. */ APRIL, /** * The singleton instance for the month of May with 31 days. * This has the numeric value of {@code 5}. */ MAY, /** * The singleton instance for the month of June with 30 days. * This has the numeric value of {@code 6}. */ JUNE, /** * The singleton instance for the month of July with 31 days. * This has the numeric value of {@code 7}. */ JULY, /** * The singleton instance for the month of August with 31 days. * This has the numeric value of {@code 8}. */ AUGUST, /** * The singleton instance for the month of September with 30 days. * This has the numeric value of {@code 9}. */ SEPTEMBER, /** * The singleton instance for the month of October with 31 days. * This has the numeric value of {@code 10}. */ OCTOBER, /** * The singleton instance for the month of November with 30 days. * This has the numeric value of {@code 11}. */ NOVEMBER, /** * The singleton instance for the month of December with 31 days. * This has the numeric value of {@code 12}. */ DECEMBER; /** * Private cache of all the constants. */ private static final Month[] ENUMS = Month.values(); //----------------------------------------------------------------------- /** * Obtains an instance of {@code Month} from an {@code int} value. *
* {@code Month} is an enum representing the 12 months of the year. * This factory allows the enum to be obtained from the {@code int} value. * The {@code int} value follows the ISO-8601 standard, from 1 (January) to 12 (December). * * @param month the month-of-year to represent, from 1 (January) to 12 (December) * @return the month-of-year, not null * @throws DateTimeException if the month-of-year is invalid */ public static Month of(int month) { if (month < 1 || month > 12) { throw new DateTimeException("Invalid value for MonthOfYear: " + month); } return ENUMS[month - 1]; } //----------------------------------------------------------------------- /** * Obtains an instance of {@code Month} from a temporal object. *
* This obtains a month based on the specified temporal. * A {@code TemporalAccessor} represents an arbitrary set of date and time information, * which this factory converts to an instance of {@code Month}. *
* The conversion extracts the {@link ChronoField#MONTH_OF_YEAR MONTH_OF_YEAR} field. * The extraction is only permitted if the temporal object has an ISO * chronology, or can be converted to a {@code LocalDate}. *
* This method matches the signature of the functional interface {@link TemporalQuery} * allowing it to be used as a query via method reference, {@code Month::from}. * * @param temporal the temporal object to convert, not null * @return the month-of-year, not null * @throws DateTimeException if unable to convert to a {@code Month} */ public static Month from(TemporalAccessor temporal) { if (temporal instanceof Month) { return (Month) temporal; } try { if (IsoChronology.INSTANCE.equals(Chronology.from(temporal)) == false) { temporal = LocalDate.from(temporal); } return of(temporal.get(MONTH_OF_YEAR)); } catch (DateTimeException ex) { throw new DateTimeException("Unable to obtain Month from TemporalAccessor: " + temporal + " of type " + temporal.getClass().getName(), ex); } } //----------------------------------------------------------------------- /** * Gets the month-of-year {@code int} value. *
* The values are numbered following the ISO-8601 standard, * from 1 (January) to 12 (December). * * @return the month-of-year, from 1 (January) to 12 (December) */ public int getValue() { return ordinal() + 1; } //----------------------------------------------------------------------- /** * Gets the textual representation, such as 'Jan' or 'December'. *
* This returns the textual name used to identify the month-of-year, * suitable for presentation to the user. * The parameters control the style of the returned text and the locale. *
* If no textual mapping is found then the {@link #getValue() numeric value} is returned. * * @param style the length of the text required, not null * @param locale the locale to use, not null * @return the text value of the month-of-year, not null */ public String getDisplayName(TextStyle style, Locale locale) { return new DateTimeFormatterBuilder().appendText(MONTH_OF_YEAR, style).toFormatter(locale).format(this); } //----------------------------------------------------------------------- /** * Checks if the specified field is supported. *
* This checks if this month-of-year can be queried for the specified field. * If false, then calling the {@link #range(TemporalField) range} and * {@link #get(TemporalField) get} methods will throw an exception. *
* If the field is {@link ChronoField#MONTH_OF_YEAR MONTH_OF_YEAR} then * this method returns true. * All other {@code ChronoField} instances will return false. *
* If the field is not a {@code ChronoField}, then the result of this method * is obtained by invoking {@code TemporalField.isSupportedBy(TemporalAccessor)} * passing {@code this} as the argument. * Whether the field is supported is determined by the field. * * @param field the field to check, null returns false * @return true if the field is supported on this month-of-year, false if not */ @Override public boolean isSupported(TemporalField field) { if (field instanceof ChronoField) { return field == MONTH_OF_YEAR; } return field != null && field.isSupportedBy(this); } /** * Gets the range of valid values for the specified field. *
* The range object expresses the minimum and maximum valid values for a field. * This month is used to enhance the accuracy of the returned range. * If it is not possible to return the range, because the field is not supported * or for some other reason, an exception is thrown. *
* If the field is {@link ChronoField#MONTH_OF_YEAR MONTH_OF_YEAR} then the * range of the month-of-year, from 1 to 12, will be returned. * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}. *
* If the field is not a {@code ChronoField}, then the result of this method * is obtained by invoking {@code TemporalField.rangeRefinedBy(TemporalAccessor)} * passing {@code this} as the argument. * Whether the range can be obtained is determined by the field. * * @param field the field to query the range for, not null * @return the range of valid values for the field, not null * @throws DateTimeException if the range for the field cannot be obtained * @throws UnsupportedTemporalTypeException if the field is not supported */ @Override public ValueRange range(TemporalField field) { if (field == MONTH_OF_YEAR) { return field.range(); } return TemporalAccessor.super.range(field); } /** * Gets the value of the specified field from this month-of-year as an {@code int}. *
* This queries this month for the value of the specified field. * The returned value will always be within the valid range of values for the field. * If it is not possible to return the value, because the field is not supported * or for some other reason, an exception is thrown. *
* If the field is {@link ChronoField#MONTH_OF_YEAR MONTH_OF_YEAR} then the * value of the month-of-year, from 1 to 12, will be returned. * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}. *
* If the field is not a {@code ChronoField}, then the result of this method * is obtained by invoking {@code TemporalField.getFrom(TemporalAccessor)} * passing {@code this} as the argument. Whether the value can be obtained, * and what the value represents, is determined by the field. * * @param field the field to get, not null * @return the value for the field, within the valid range of values * @throws DateTimeException if a value for the field cannot be obtained or * the value is outside the range of valid values for the field * @throws UnsupportedTemporalTypeException if the field is not supported or * the range of values exceeds an {@code int} * @throws ArithmeticException if numeric overflow occurs */ @Override public int get(TemporalField field) { if (field == MONTH_OF_YEAR) { return getValue(); } return TemporalAccessor.super.get(field); } /** * Gets the value of the specified field from this month-of-year as a {@code long}. *
* This queries this month for the value of the specified field. * If it is not possible to return the value, because the field is not supported * or for some other reason, an exception is thrown. *
* If the field is {@link ChronoField#MONTH_OF_YEAR MONTH_OF_YEAR} then the * value of the month-of-year, from 1 to 12, will be returned. * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}. *
* If the field is not a {@code ChronoField}, then the result of this method * is obtained by invoking {@code TemporalField.getFrom(TemporalAccessor)} * passing {@code this} as the argument. Whether the value can be obtained, * and what the value represents, is determined by the field. * * @param field the field to get, not null * @return the value for the field * @throws DateTimeException if a value for the field cannot be obtained * @throws UnsupportedTemporalTypeException if the field is not supported * @throws ArithmeticException if numeric overflow occurs */ @Override public long getLong(TemporalField field) { if (field == MONTH_OF_YEAR) { return getValue(); } else if (field instanceof ChronoField) { throw new UnsupportedTemporalTypeException("Unsupported field: " + field); } return field.getFrom(this); } //----------------------------------------------------------------------- /** * Returns the month-of-year that is the specified number of quarters after this one. *
* The calculation rolls around the end of the year from December to January. * The specified period may be negative. *
* This instance is immutable and unaffected by this method call. * * @param months the months to add, positive or negative * @return the resulting month, not null */ public Month plus(long months) { int amount = (int) (months % 12); return ENUMS[(ordinal() + (amount + 12)) % 12]; } /** * Returns the month-of-year that is the specified number of months before this one. *
* The calculation rolls around the start of the year from January to December. * The specified period may be negative. *
* This instance is immutable and unaffected by this method call. * * @param months the months to subtract, positive or negative * @return the resulting month, not null */ public Month minus(long months) { return plus(-(months % 12)); } //----------------------------------------------------------------------- /** * Gets the length of this month in days. *
* This takes a flag to determine whether to return the length for a leap year or not. *
* February has 28 days in a standard year and 29 days in a leap year. * April, June, September and November have 30 days. * All other months have 31 days. * * @param leapYear true if the length is required for a leap year * @return the length of this month in days, from 28 to 31 */ public int length(boolean leapYear) { switch (this) { case FEBRUARY: return (leapYear ? 29 : 28); case APRIL: case JUNE: case SEPTEMBER: case NOVEMBER: return 30; default: return 31; } } /** * Gets the minimum length of this month in days. *
* February has a minimum length of 28 days. * April, June, September and November have 30 days. * All other months have 31 days. * * @return the minimum length of this month in days, from 28 to 31 */ public int minLength() { switch (this) { case FEBRUARY: return 28; case APRIL: case JUNE: case SEPTEMBER: case NOVEMBER: return 30; default: return 31; } } /** * Gets the maximum length of this month in days. *
* February has a maximum length of 29 days. * April, June, September and November have 30 days. * All other months have 31 days. * * @return the maximum length of this month in days, from 29 to 31 */ public int maxLength() { switch (this) { case FEBRUARY: return 29; case APRIL: case JUNE: case SEPTEMBER: case NOVEMBER: return 30; default: return 31; } } //----------------------------------------------------------------------- /** * Gets the day-of-year corresponding to the first day of this month. *
* This returns the day-of-year that this month begins on, using the leap * year flag to determine the length of February. * * @param leapYear true if the length is required for a leap year * @return the day of year corresponding to the first day of this month, from 1 to 336 */ public int firstDayOfYear(boolean leapYear) { int leap = leapYear ? 1 : 0; switch (this) { case JANUARY: return 1; case FEBRUARY: return 32; case MARCH: return 60 + leap; case APRIL: return 91 + leap; case MAY: return 121 + leap; case JUNE: return 152 + leap; case JULY: return 182 + leap; case AUGUST: return 213 + leap; case SEPTEMBER: return 244 + leap; case OCTOBER: return 274 + leap; case NOVEMBER: return 305 + leap; case DECEMBER: default: return 335 + leap; } } /** * Gets the month corresponding to the first month of this quarter. *
* The year can be divided into four quarters. * This method returns the first month of the quarter for the base month. * January, February and March return January. * April, May and June return April. * July, August and September return July. * October, November and December return October. * * @return the first month of the quarter corresponding to this month, not null */ public Month firstMonthOfQuarter() { return ENUMS[(ordinal() / 3) * 3]; } //----------------------------------------------------------------------- /** * Queries this month-of-year using the specified query. *
* This queries this month-of-year using the specified query strategy object. * The {@code TemporalQuery} object defines the logic to be used to * obtain the result. Read the documentation of the query to understand * what the result of this method will be. *
* The result of this method is obtained by invoking the
* {@link TemporalQuery#queryFrom(TemporalAccessor)} method on the
* specified query passing {@code this} as the argument.
*
* @param
* This returns a temporal object of the same observable type as the input
* with the month-of-year changed to be the same as this.
*
* The adjustment is equivalent to using {@link Temporal#with(TemporalField, long)}
* passing {@link ChronoField#MONTH_OF_YEAR} as the field.
* If the specified temporal object does not use the ISO calendar system then
* a {@code DateTimeException} is thrown.
*
* In most cases, it is clearer to reverse the calling pattern by using
* {@link Temporal#with(TemporalAdjuster)}:
*
* For example, given a date in May, the following are output:
*
* This instance is immutable and unaffected by this method call.
*
* @param temporal the target object to be adjusted, not null
* @return the adjusted object, not null
* @throws DateTimeException if unable to make the adjustment
* @throws ArithmeticException if numeric overflow occurs
*/
@Override
public Temporal adjustInto(Temporal temporal) {
if (Chronology.from(temporal).equals(IsoChronology.INSTANCE) == false) {
throw new DateTimeException("Adjustment only supported on ISO date-time");
}
return temporal.with(MONTH_OF_YEAR, getValue());
}
}
* // these two lines are equivalent, but the second approach is recommended
* temporal = thisMonth.adjustInto(temporal);
* temporal = temporal.with(thisMonth);
*
*
* dateInMay.with(JANUARY); // four months earlier
* dateInMay.with(APRIL); // one months earlier
* dateInMay.with(MAY); // same date
* dateInMay.with(JUNE); // one month later
* dateInMay.with(DECEMBER); // seven months later
*
*