+ * {@code MonthDay} is an immutable date-time object that represents the combination + * of a year and month. Any field that can be derived from a month and day, such as + * quarter-of-year, can be obtained. + *
+ * This class does not store or represent a year, time or time-zone. + * For example, the value "December 3rd" can be stored in a {@code MonthDay}. + *
+ * Since a {@code MonthDay} does not possess a year, the leap day of + * February 29th is considered valid. + *
+ * This class implements {@link TemporalAccessor} rather than {@link Temporal}. + * This is because it is not possible to define whether February 29th is valid or not + * without external information, preventing the implementation of plus/minus. + * Related to this, {@code MonthDay} only provides access to query and set the fields + * {@code MONTH_OF_YEAR} and {@code DAY_OF_MONTH}. + *
+ * The ISO-8601 calendar system is the modern civil calendar system used today + * in most of the world. It is equivalent to the proleptic Gregorian calendar + * system, in which today's rules for leap years are applied for all time. + * For most applications written today, the ISO-8601 rules are entirely suitable. + * However, any application that makes use of historical dates, and requires them + * to be accurate will find the ISO-8601 approach unsuitable. + * + *
+ * This will query the {@link java.time.Clock#systemDefaultZone() system clock} in the default + * time-zone to obtain the current month-day. + *
+ * Using this method will prevent the ability to use an alternate clock for testing + * because the clock is hard-coded. + * + * @return the current month-day using the system clock and default time-zone, not null + */ + public static MonthDay now() { + return now(Clock.systemDefaultZone()); + } + + /** + * Obtains the current month-day from the system clock in the specified time-zone. + *
+ * This will query the {@link Clock#system(java.time.ZoneId) system clock} to obtain the current month-day. + * Specifying the time-zone avoids dependence on the default time-zone. + *
+ * Using this method will prevent the ability to use an alternate clock for testing + * because the clock is hard-coded. + * + * @param zone the zone ID to use, not null + * @return the current month-day using the system clock, not null + */ + public static MonthDay now(ZoneId zone) { + return now(Clock.system(zone)); + } + + /** + * Obtains the current month-day from the specified clock. + *
+ * This will query the specified clock to obtain the current month-day. + * Using this method allows the use of an alternate clock for testing. + * The alternate clock may be introduced using {@link Clock dependency injection}. + * + * @param clock the clock to use, not null + * @return the current month-day, not null + */ + public static MonthDay now(Clock clock) { + final LocalDate now = LocalDate.now(clock); // called once + return MonthDay.of(now.getMonth(), now.getDayOfMonth()); + } + + //----------------------------------------------------------------------- + /** + * Obtains an instance of {@code MonthDay}. + *
+ * The day-of-month must be valid for the month within a leap year. + * Hence, for February, day 29 is valid. + *
+ * For example, passing in April and day 31 will throw an exception, as + * there can never be April 31st in any year. By contrast, passing in + * February 29th is permitted, as that month-day can sometimes be valid. + * + * @param month the month-of-year to represent, not null + * @param dayOfMonth the day-of-month to represent, from 1 to 31 + * @return the month-day, not null + * @throws DateTimeException if the value of any field is out of range + * @throws DateTimeException if the day-of-month is invalid for the month + */ + public static MonthDay of(Month month, int dayOfMonth) { + Objects.requireNonNull(month, "month"); + DAY_OF_MONTH.checkValidValue(dayOfMonth); + if (dayOfMonth > month.maxLength()) { + throw new DateTimeException("Illegal value for DayOfMonth field, value " + dayOfMonth + + " is not valid for month " + month.name()); + } + return new MonthDay(month.getValue(), dayOfMonth); + } + + /** + * Obtains an instance of {@code MonthDay}. + *
+ * The day-of-month must be valid for the month within a leap year. + * Hence, for month 2 (February), day 29 is valid. + *
+ * For example, passing in month 4 (April) and day 31 will throw an exception, as + * there can never be April 31st in any year. By contrast, passing in + * February 29th is permitted, as that month-day can sometimes be valid. + * + * @param month the month-of-year to represent, from 1 (January) to 12 (December) + * @param dayOfMonth the day-of-month to represent, from 1 to 31 + * @return the month-day, not null + * @throws DateTimeException if the value of any field is out of range + * @throws DateTimeException if the day-of-month is invalid for the month + */ + public static MonthDay of(int month, int dayOfMonth) { + return of(Month.of(month), dayOfMonth); + } + + //----------------------------------------------------------------------- + /** + * Obtains an instance of {@code MonthDay} 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 MonthDay}. + *
+ * The conversion extracts the {@link ChronoField#MONTH_OF_YEAR MONTH_OF_YEAR} and + * {@link ChronoField#DAY_OF_MONTH DAY_OF_MONTH} fields. + * The extraction is only permitted if the date-time has an ISO chronology. + *
+ * This method matches the signature of the functional interface {@link TemporalQuery} + * allowing it to be used in queries via method reference, {@code MonthDay::from}. + * + * @param temporal the temporal object to convert, not null + * @return the month-day, not null + * @throws DateTimeException if unable to convert to a {@code MonthDay} + */ + public static MonthDay from(TemporalAccessor temporal) { + if (temporal instanceof MonthDay) { + return (MonthDay) temporal; + } + try { + if (ISOChrono.INSTANCE.equals(Chrono.from(temporal)) == false) { + temporal = LocalDate.from(temporal); + } + return of(temporal.get(MONTH_OF_YEAR), temporal.get(DAY_OF_MONTH)); + } catch (DateTimeException ex) { + throw new DateTimeException("Unable to obtain MonthDay from TemporalAccessor: " + temporal.getClass(), ex); + } + } + + //----------------------------------------------------------------------- + /** + * Obtains an instance of {@code MonthDay} from a text string such as {@code --12-03}. + *
+ * The string must represent a valid month-day. + * The format is {@code --MM-dd}. + * + * @param text the text to parse such as "--12-03", not null + * @return the parsed month-day, not null + * @throws DateTimeParseException if the text cannot be parsed + */ + public static MonthDay parse(CharSequence text) { + return parse(text, PARSER); + } + + /** + * Obtains an instance of {@code MonthDay} from a text string using a specific formatter. + *
+ * The text is parsed using the formatter, returning a month-day. + * + * @param text the text to parse, not null + * @param formatter the formatter to use, not null + * @return the parsed month-day, not null + * @throws DateTimeParseException if the text cannot be parsed + */ + public static MonthDay parse(CharSequence text, DateTimeFormatter formatter) { + Objects.requireNonNull(formatter, "formatter"); + return formatter.parse(text, MonthDay::from); + } + + //----------------------------------------------------------------------- + /** + * Constructor, previously validated. + * + * @param month the month-of-year to represent, validated from 1 to 12 + * @param dayOfMonth the day-of-month to represent, validated from 1 to 29-31 + */ + private MonthDay(int month, int dayOfMonth) { + this.month = month; + this.day = dayOfMonth; + } + + //----------------------------------------------------------------------- + /** + * Checks if the specified field is supported. + *
+ * This checks if this month-day 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 a {@link ChronoField} then the query is implemented here. + * The {@link #isSupported(TemporalField) supported fields} will return valid + * values based on this date-time. + * The supported fields are: + *
+ * 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-day, false if not + */ + @Override + public boolean isSupported(TemporalField field) { + if (field instanceof ChronoField) { + return field == MONTH_OF_YEAR || field == DAY_OF_MONTH; + } + 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-day 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 a {@link ChronoField} then the query is implemented here. + * The {@link #isSupported(TemporalField) supported fields} will return + * appropriate range instances. + * 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(); + } else if (field == DAY_OF_MONTH) { + return ValueRange.of(1, getMonth().minLength(), getMonth().maxLength()); + } + return TemporalAccessor.super.range(field); + } + + /** + * Gets the value of the specified field from this month-day as an {@code int}. + *
+ * This queries this month-day 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 a {@link ChronoField} then the query is implemented here. + * The {@link #isSupported(TemporalField) supported fields} will return valid + * values based on this month-day. + * 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 // override for Javadoc + public int get(TemporalField field) { + return range(field).checkValidIntValue(getLong(field), field); + } + + /** + * Gets the value of the specified field from this month-day as a {@code long}. + *
+ * This queries this month-day 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 a {@link ChronoField} then the query is implemented here. + * The {@link #isSupported(TemporalField) supported fields} will return valid + * values based on this month-day. + * 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 instanceof ChronoField) { + switch ((ChronoField) field) { + // alignedDOW and alignedWOM not supported because they cannot be set in with() + case DAY_OF_MONTH: return day; + case MONTH_OF_YEAR: return month; + } + throw new DateTimeException("Unsupported field: " + field.getName()); + } + return field.doGet(this); + } + + //----------------------------------------------------------------------- + /** + * Gets the month-of-year field using the {@code Month} enum. + *
+ * This method returns the enum {@link Month} for the month. + * This avoids confusion as to what {@code int} values mean. + * If you need access to the primitive {@code int} value then the enum + * provides the {@link Month#getValue() int value}. + * + * @return the month-of-year, not null + */ + public Month getMonth() { + return Month.of(month); + } + + /** + * Gets the day-of-month field. + *
+ * This method returns the primitive {@code int} value for the day-of-month. + * + * @return the day-of-month, from 1 to 31 + */ + public int getDayOfMonth() { + return day; + } + + //----------------------------------------------------------------------- + /** + * Checks if the year is valid for this month-day. + *
+ * This method checks whether this month and day and the input year form + * a valid date. This can only return false for February 29th. + * + * @param year the year to validate, an out of range value returns false + * @return true if the year is valid for this month-day + * @see Year#isValidMonthDay(MonthDay) + */ + public boolean isValidYear(int year) { + return (day == 29 && month == 2 && Year.isLeap(year) == false) == false; + } + + //----------------------------------------------------------------------- + /** + * Returns a copy of this {@code MonthDay} with the month-of-year altered. + *
+ * This returns a month-day with the specified month. + * If the day-of-month is invalid for the specified month, the day will + * be adjusted to the last valid day-of-month. + *
+ * This instance is immutable and unaffected by this method call. + * + * @param month the month-of-year to set in the returned month-day, from 1 (January) to 12 (December) + * @return a {@code MonthDay} based on this month-day with the requested month, not null + * @throws DateTimeException if the month-of-year value is invalid + */ + public MonthDay withMonth(int month) { + return with(Month.of(month)); + } + + /** + * Returns a copy of this {@code MonthDay} with the month-of-year altered. + *
+ * This returns a month-day with the specified month. + * If the day-of-month is invalid for the specified month, the day will + * be adjusted to the last valid day-of-month. + *
+ * This instance is immutable and unaffected by this method call. + * + * @param month the month-of-year to set in the returned month-day, not null + * @return a {@code MonthDay} based on this month-day with the requested month, not null + */ + public MonthDay with(Month month) { + Objects.requireNonNull(month, "month"); + if (month.getValue() == this.month) { + return this; + } + int day = Math.min(this.day, month.maxLength()); + return new MonthDay(month.getValue(), day); + } + + /** + * Returns a copy of this {@code MonthDay} with the day-of-month altered. + *
+ * This returns a month-day with the specified day-of-month. + * If the day-of-month is invalid for the month, an exception is thrown. + *
+ * This instance is immutable and unaffected by this method call. + * + * @param dayOfMonth the day-of-month to set in the return month-day, from 1 to 31 + * @return a {@code MonthDay} based on this month-day with the requested day, not null + * @throws DateTimeException if the day-of-month value is invalid + * @throws DateTimeException if the day-of-month is invalid for the month + */ + public MonthDay withDayOfMonth(int dayOfMonth) { + if (dayOfMonth == this.day) { + return this; + } + return of(month, dayOfMonth); + } + + //----------------------------------------------------------------------- + /** + * Queries this month-day using the specified query. + *
+ * This queries this month-day 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 and day-of-month changed to be the same as this.
+ *
+ * The adjustment is equivalent to using {@link Temporal#with(TemporalField, long)}
+ * twice, passing {@link ChronoField#MONTH_OF_YEAR} and
+ * {@link ChronoField#DAY_OF_MONTH} as the fields.
+ * 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)}:
+ *
+ * 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");
+ }
+ temporal = temporal.with(MONTH_OF_YEAR, month);
+ return temporal.with(DAY_OF_MONTH, Math.min(temporal.range(DAY_OF_MONTH).getMaximum(), day));
+ }
+
+ //-----------------------------------------------------------------------
+ /**
+ * Returns a date formed from this month-day at the specified year.
+ *
+ * This combines this month-day and the specified year to form a {@code LocalDate}.
+ * A month-day of February 29th will be adjusted to February 28th in the resulting
+ * date if the year is not a leap year.
+ *
+ * This instance is immutable and unaffected by this method call.
+ *
+ * @param year the year to use, from MIN_YEAR to MAX_YEAR
+ * @return the local date formed from this month-day and the specified year, not null
+ * @see Year#atMonthDay(MonthDay)
+ */
+ public LocalDate atYear(int year) {
+ return LocalDate.of(year, month, isValidYear(year) ? day : 28);
+ }
+
+ //-----------------------------------------------------------------------
+ /**
+ * Compares this month-day to another month-day.
+ *
+ * The comparison is based first on value of the month, then on the value of the day.
+ * It is "consistent with equals", as defined by {@link Comparable}.
+ *
+ * @param other the other month-day to compare to, not null
+ * @return the comparator value, negative if less, positive if greater
+ */
+ public int compareTo(MonthDay other) {
+ int cmp = (month - other.month);
+ if (cmp == 0) {
+ cmp = (day - other.day);
+ }
+ return cmp;
+ }
+
+ /**
+ * Is this month-day after the specified month-day.
+ *
+ * @param other the other month-day to compare to, not null
+ * @return true if this is after the specified month-day
+ */
+ public boolean isAfter(MonthDay other) {
+ return compareTo(other) > 0;
+ }
+
+ /**
+ * Is this month-day before the specified month-day.
+ *
+ * @param other the other month-day to compare to, not null
+ * @return true if this point is before the specified month-day
+ */
+ public boolean isBefore(MonthDay other) {
+ return compareTo(other) < 0;
+ }
+
+ //-----------------------------------------------------------------------
+ /**
+ * Checks if this month-day is equal to another month-day.
+ *
+ * The comparison is based on the time-line position of the month-day within a year.
+ *
+ * @param obj the object to check, null returns false
+ * @return true if this is equal to the other month-day
+ */
+ @Override
+ public boolean equals(Object obj) {
+ if (this == obj) {
+ return true;
+ }
+ if (obj instanceof MonthDay) {
+ MonthDay other = (MonthDay) obj;
+ return month == other.month && day == other.day;
+ }
+ return false;
+ }
+
+ /**
+ * A hash code for this month-day.
+ *
+ * @return a suitable hash code
+ */
+ @Override
+ public int hashCode() {
+ return (month << 6) + day;
+ }
+
+ //-----------------------------------------------------------------------
+ /**
+ * Outputs this month-day as a {@code String}, such as {@code --12-03}.
+ *
+ * The output will be in the format {@code --MM-dd}:
+ *
+ * @return a string representation of this month-day, not null
+ */
+ @Override
+ public String toString() {
+ return new StringBuilder(10).append("--")
+ .append(month < 10 ? "0" : "").append(month)
+ .append(day < 10 ? "-0" : "-").append(day)
+ .toString();
+ }
+
+ /**
+ * Outputs this month-day as a {@code String} using the formatter.
+ *
+ * This month-day will be passed to the formatter
+ * {@link DateTimeFormatter#print(TemporalAccessor) print method}.
+ *
+ * @param formatter the formatter to use, not null
+ * @return the formatted month-day string, not null
+ * @throws DateTimeException if an error occurs during printing
+ */
+ public String toString(DateTimeFormatter formatter) {
+ Objects.requireNonNull(formatter, "formatter");
+ return formatter.print(this);
+ }
+
+ //-----------------------------------------------------------------------
+ /**
+ * Writes the object using a
+ * dedicated serialized form.
+ *
+ * // these two lines are equivalent, but the second approach is recommended
+ * temporal = thisMonthDay.adjustInto(temporal);
+ * temporal = temporal.with(thisMonthDay);
+ *
+ *
+ * out.writeByte(6); // identifies this as a Year
+ * out.writeByte(month);
+ * out.writeByte(day);
+ *
+ *
+ * @return the instance of {@code Ser}, not null
+ */
+ private Object writeReplace() {
+ return new Ser(Ser.MONTH_DAY_TYPE, this);
+ }
+
+ /**
+ * Defend against malicious streams.
+ * @return never
+ * @throws InvalidObjectException always
+ */
+ private Object readResolve() throws ObjectStreamException {
+ throw new InvalidObjectException("Deserialization via serialization delegate");
+ }
+
+ void writeExternal(DataOutput out) throws IOException {
+ out.writeByte(month);
+ out.writeByte(day);
+ }
+
+ static MonthDay readExternal(DataInput in) throws IOException {
+ byte month = in.readByte();
+ byte day = in.readByte();
+ return MonthDay.of(month, day);
+ }
+
+}