Month (Java Platform SE 8 )
Keywords: java.time.Month class
Date: 2015-11-18

compact1, compact2, compact3
java.time

## Enum Month

- java.lang.Object
- - java.lang.Enum<Month>
  - - java.time.Month

- All Implemented Interfaces:
    Serializable, Comparable<Month>, TemporalAccessor, TemporalAdjuster

      public enum Month
      extends Enum<Month>
      implements TemporalAccessor, TemporalAdjuster

  A month-of-year, such as 'July'.

  `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 `int` value. The `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 `int` value to ensure code clarity.

  Do not use `ordinal()` to obtain the numeric representation of `Month`. Use `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.

  Implementation Requirements:
    This is an immutable and thread-safe enum.
  Since:
    1.8

- - ### Enum Constant Summary

    Enum Constants
    Enum Constant and Description
    `APRIL` The singleton instance for the month of April with 30 days.
    `AUGUST` The singleton instance for the month of August with 31 days.
    `DECEMBER` The singleton instance for the month of December with 31 days.
    `FEBRUARY` The singleton instance for the month of February with 28 days, or 29 in a leap year.
    `JANUARY` The singleton instance for the month of January with 31 days.
    `JULY` The singleton instance for the month of July with 31 days.
    `JUNE` The singleton instance for the month of June with 30 days.
    `MARCH` The singleton instance for the month of March with 31 days.
    `MAY` The singleton instance for the month of May with 31 days.
    `NOVEMBER` The singleton instance for the month of November with 30 days.
    `OCTOBER` The singleton instance for the month of October with 31 days.
    `SEPTEMBER` The singleton instance for the month of September with 30 days.

  - ### Method Summary

    All Methods Static Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `Temporal` | `adjustInto(Temporal temporal)` Adjusts the specified temporal object to have this month-of-year.
    `int` | `firstDayOfYear(boolean leapYear)` Gets the day-of-year corresponding to the first day of this month.
    `Month` | `firstMonthOfQuarter()` Gets the month corresponding to the first month of this quarter.
    `static Month` | `from(TemporalAccessor temporal)` Obtains an instance of `Month` from a temporal object.
    `int` | `get(TemporalField field)` Gets the value of the specified field from this month-of-year as an `int`.
    `String` | `getDisplayName(TextStyle style, Locale locale)` Gets the textual representation, such as 'Jan' or 'December'.
    `long` | `getLong(TemporalField field)` Gets the value of the specified field from this month-of-year as a `long`.
    `int` | `getValue()` Gets the month-of-year `int` value.
    `boolean` | `isSupported(TemporalField field)` Checks if the specified field is supported.
    `int` | `length(boolean leapYear)` Gets the length of this month in days.
    `int` | `maxLength()` Gets the maximum length of this month in days.
    `int` | `minLength()` Gets the minimum length of this month in days.
    `Month` | `minus(long months)` Returns the month-of-year that is the specified number of months before this one.
    `static Month` | `of(int month)` Obtains an instance of `Month` from an `int` value.
    `Month` | `plus(long months)` Returns the month-of-year that is the specified number of quarters after this one.
    `<R> R` | `query(TemporalQuery<R> query)` Queries this month-of-year using the specified query.
    `ValueRange` | `range(TemporalField field)` Gets the range of valid values for the specified field.
    `static Month` | `valueOf(String name)` Returns the enum constant of this type with the specified name.
    `static Month[]` | `values()` Returns an array containing the constants of this enum type, in the order they are declared.

    - ### Methods inherited from class java.lang.Enum

      `clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf`

    - ### Methods inherited from class java.lang.Object

      `getClass, notify, notifyAll, wait, wait, wait`

- - ### Enum Constant Detail

    - #### JANUARY

          public static final Month JANUARY

      The singleton instance for the month of January with 31 days. This has the numeric value of `1`.

    - #### FEBRUARY

          public static final Month FEBRUARY

      The singleton instance for the month of February with 28 days, or 29 in a leap year. This has the numeric value of `2`.

    - #### MARCH

          public static final Month MARCH

      The singleton instance for the month of March with 31 days. This has the numeric value of `3`.

    - #### APRIL

          public static final Month APRIL

      The singleton instance for the month of April with 30 days. This has the numeric value of `4`.

    - #### MAY

          public static final Month MAY

      The singleton instance for the month of May with 31 days. This has the numeric value of `5`.

    - #### JUNE

          public static final Month JUNE

      The singleton instance for the month of June with 30 days. This has the numeric value of `6`.

    - #### JULY

          public static final Month JULY

      The singleton instance for the month of July with 31 days. This has the numeric value of `7`.

    - #### AUGUST

          public static final Month AUGUST

      The singleton instance for the month of August with 31 days. This has the numeric value of `8`.

    - #### SEPTEMBER

          public static final Month SEPTEMBER

      The singleton instance for the month of September with 30 days. This has the numeric value of `9`.

    - #### OCTOBER

          public static final Month OCTOBER

      The singleton instance for the month of October with 31 days. This has the numeric value of `10`.

    - #### NOVEMBER

          public static final Month NOVEMBER

      The singleton instance for the month of November with 30 days. This has the numeric value of `11`.

    - #### DECEMBER

          public static final Month DECEMBER

      The singleton instance for the month of December with 31 days. This has the numeric value of `12`.

  - ### Method Detail

    - #### values

          public static Month[] values()

      Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows:

          for (Month c : Month.values())
              System.out.println(c);

      Returns:
        an array containing the constants of this enum type, in the order they are declared

    - #### valueOf

          public static Month valueOf(String name)

      Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)
      Parameters:
        `name` - the name of the enum constant to be returned.
      Returns:
        the enum constant with the specified name
      Throws:
        `IllegalArgumentException` - if this enum type has no constant with the specified name
        `NullPointerException` - if the argument is null

    - #### of

          public static Month of(int month)

      Obtains an instance of `Month` from an `int` value.

      `Month` is an enum representing the 12 months of the year. This factory allows the enum to be obtained from the `int` value. The `int` value follows the ISO-8601 standard, from 1 (January) to 12 (December).

      Parameters:
        `month` - the month-of-year to represent, from 1 (January) to 12 (December)
      Returns:
        the month-of-year, not null
      Throws:
        `DateTimeException` - if the month-of-year is invalid

    - #### from

          public static Month from(TemporalAccessor temporal)

      Obtains an instance of `Month` from a temporal object.

      This obtains a month based on the specified temporal. A `TemporalAccessor` represents an arbitrary set of date and time information, which this factory converts to an instance of `Month`.

      The conversion extracts the `MONTH_OF_YEAR` field. The extraction is only permitted if the temporal object has an ISO chronology, or can be converted to a `LocalDate`.

      This method matches the signature of the functional interface `TemporalQuery` allowing it to be used as a query via method reference, `Month::from`.

      Parameters:
        `temporal` - the temporal object to convert, not null
      Returns:
        the month-of-year, not null
      Throws:
        `DateTimeException` - if unable to convert to a `Month`

    - #### getValue

          public int getValue()

      Gets the month-of-year `int` value.

      The values are numbered following the ISO-8601 standard, from 1 (January) to 12 (December).

      Returns:
        the month-of-year, from 1 (January) to 12 (December)

    - #### getDisplayName

          public String getDisplayName(TextStyle style,
                                       Locale locale)

      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 `numeric value` is returned.

      Parameters:
        `style` - the length of the text required, not null
        `locale` - the locale to use, not null
      Returns:
        the text value of the month-of-year, not null

    - #### isSupported

          public boolean isSupported(TemporalField field)

      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 `range` and `get` methods will throw an exception.

      If the field is `MONTH_OF_YEAR` then this method returns true. All other `ChronoField` instances will return false.

      If the field is not a `ChronoField`, then the result of this method is obtained by invoking `TemporalField.isSupportedBy(TemporalAccessor)` passing `this` as the argument. Whether the field is supported is determined by the field.

      Specified by:
        `isSupported` in interface `TemporalAccessor`
      Parameters:
        `field` - the field to check, null returns false
      Returns:
        true if the field is supported on this month-of-year, false if not

    - #### range

          public ValueRange range(TemporalField field)

      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 `MONTH_OF_YEAR` then the range of the month-of-year, from 1 to 12, will be returned. All other `ChronoField` instances will throw an `UnsupportedTemporalTypeException`.

      If the field is not a `ChronoField`, then the result of this method is obtained by invoking `TemporalField.rangeRefinedBy(TemporalAccessor)` passing `this` as the argument. Whether the range can be obtained is determined by the field.

      Specified by:
        `range` in interface `TemporalAccessor`
      Parameters:
        `field` - the field to query the range for, not null
      Returns:
        the range of valid values for the field, not null
      Throws:
        `DateTimeException` - if the range for the field cannot be obtained
        `UnsupportedTemporalTypeException` - if the field is not supported

    - #### get

          public int get(TemporalField field)

      Gets the value of the specified field from this month-of-year as an `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 `MONTH_OF_YEAR` then the value of the month-of-year, from 1 to 12, will be returned. All other `ChronoField` instances will throw an `UnsupportedTemporalTypeException`.

      If the field is not a `ChronoField`, then the result of this method is obtained by invoking `TemporalField.getFrom(TemporalAccessor)` passing `this` as the argument. Whether the value can be obtained, and what the value represents, is determined by the field.

      Specified by:
        `get` in interface `TemporalAccessor`
      Parameters:
        `field` - the field to get, not null
      Returns:
        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
        `UnsupportedTemporalTypeException` - if the field is not supported or the range of values exceeds an `int`
        `ArithmeticException` - if numeric overflow occurs

    - #### getLong

          public long getLong(TemporalField field)

      Gets the value of the specified field from this month-of-year as a `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 `MONTH_OF_YEAR` then the value of the month-of-year, from 1 to 12, will be returned. All other `ChronoField` instances will throw an `UnsupportedTemporalTypeException`.

      If the field is not a `ChronoField`, then the result of this method is obtained by invoking `TemporalField.getFrom(TemporalAccessor)` passing `this` as the argument. Whether the value can be obtained, and what the value represents, is determined by the field.

      Specified by:
        `getLong` in interface `TemporalAccessor`
      Parameters:
        `field` - the field to get, not null
      Returns:
        the value for the field
      Throws:
        `DateTimeException` - if a value for the field cannot be obtained
        `UnsupportedTemporalTypeException` - if the field is not supported
        `ArithmeticException` - if numeric overflow occurs

    - #### plus

          public Month plus(long months)

      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.

      Parameters:
        `months` - the months to add, positive or negative
      Returns:
        the resulting month, not null

    - #### minus

          public Month minus(long months)

      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.

      Parameters:
        `months` - the months to subtract, positive or negative
      Returns:
        the resulting month, not null

    - #### length

          public int length(boolean leapYear)

      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.

      Parameters:
        `leapYear` - true if the length is required for a leap year
      Returns:
        the length of this month in days, from 28 to 31

    - #### minLength

          public int minLength()

      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.

      Returns:
        the minimum length of this month in days, from 28 to 31

    - #### maxLength

          public int maxLength()

      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.

      Returns:
        the maximum length of this month in days, from 29 to 31

    - #### firstDayOfYear

          public int firstDayOfYear(boolean leapYear)

      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.

      Parameters:
        `leapYear` - true if the length is required for a leap year
      Returns:
        the day of year corresponding to the first day of this month, from 1 to 336

    - #### firstMonthOfQuarter

          public Month firstMonthOfQuarter()

      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.

      Returns:
        the first month of the quarter corresponding to this month, not null

    - #### query

          public <R> R query(TemporalQuery<R> query)

      Queries this month-of-year using the specified query.

      This queries this month-of-year using the specified query strategy object. The `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 `TemporalQuery.queryFrom(TemporalAccessor)` method on the specified query passing `this` as the argument.

      Specified by:
        `query` in interface `TemporalAccessor`
      Type Parameters:
        `R` - the type of the result
      Parameters:
        `query` - the query to invoke, not null
      Returns:
        the query result, null may be returned (defined by the query)
      Throws:
        `DateTimeException` - if unable to query (defined by the query)
        `ArithmeticException` - if numeric overflow occurs (defined by the query)

    - #### adjustInto

          public Temporal adjustInto(Temporal temporal)

      Adjusts the specified temporal object to have this month-of-year.

      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 `Temporal.with(TemporalField, long)` passing `ChronoField.MONTH_OF_YEAR` as the field. If the specified temporal object does not use the ISO calendar system then a `DateTimeException` is thrown.

      In most cases, it is clearer to reverse the calling pattern by using `Temporal.with(TemporalAdjuster)`:

             // these two lines are equivalent, but the second approach is recommended
             temporal = thisMonth.adjustInto(temporal);
             temporal = temporal.with(thisMonth);

      For example, given a date in May, the following are output:

             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

      This instance is immutable and unaffected by this method call.

      Specified by:
        `adjustInto` in interface `TemporalAdjuster`
      Parameters:
        `temporal` - the target object to be adjusted, not null
      Returns:
        the adjusted object, not null
      Throws:
        `DateTimeException` - if unable to make the adjustment
        `ArithmeticException` - if numeric overflow occurs

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