+ * {@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. + * + *
+ * {@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. + *
+ * A {@code TemporalAccessor} represents some form of date and time information. + * This factory converts the arbitrary temporal object 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 in queries 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 (ISOChrono.INSTANCE.equals(Chrono.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.getClass(), 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. + * The parameters control the length 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 getText(TextStyle style, Locale locale) { + return new DateTimeFormatterBuilder().appendText(MONTH_OF_YEAR, style).toFormatter(locale).print(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.doIsSupported(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.doIsSupported(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 a {@code DateTimeException}. + *
+ * If the field is not a {@code ChronoField}, then the result of this method + * is obtained by invoking {@code TemporalField.doRange(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 + */ + @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 for 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 a {@code DateTimeException}. + *
+ * If the field is not a {@code ChronoField}, then the result of this method + * is obtained by invoking {@code TemporalField.doGet(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 + * @throws DateTimeException if the range of valid values for the field exceeds an {@code int} + * @throws DateTimeException if the value is outside the range of valid values for the field + * @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 for 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 a {@code DateTimeException}. + *
+ * If the field is not a {@code ChronoField}, then the result of this method + * is obtained by invoking {@code TemporalField.doGet(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 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 DateTimeException("Unsupported field: " + field.getName()); + } + return field.doGet(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 (Chrono.from(temporal).equals(ISOChrono.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
+ *
+ *