DayOfWeek (Java Platform SE 8 )
Keywords: java.time.DayOfWeek class
Date: 2020-03-26

compact1, compact2, compact3
java.time

## Enum DayOfWeek

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

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

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

  A day-of-week, such as 'Tuesday'.

  `DayOfWeek` is an enum representing the 7 days of the week - Monday, Tuesday, Wednesday, Thursday, Friday, Saturday and Sunday.

  In addition to the textual enum name, each day-of-week has an `int` value. The `int` value follows the ISO-8601 standard, from 1 (Monday) to 7 (Sunday). It is recommended that applications use the enum rather than the `int` value to ensure code clarity.

  This enum provides access to the localized textual form of the day-of-week. Some locales also assign different numeric values to the days, declaring Sunday to have the value 1, however this class provides no support for this. See `WeekFields` for localized week-numbering.

  Do not use `ordinal()` to obtain the numeric representation of `DayOfWeek`. 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 day-of-week concept defined exactly equivalent to the ISO calendar system.

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

- - ### Enum Constant Summary

    Enum Constants
    Enum Constant and Description
    `FRIDAY` The singleton instance for the day-of-week of Friday.
    `MONDAY` The singleton instance for the day-of-week of Monday.
    `SATURDAY` The singleton instance for the day-of-week of Saturday.
    `SUNDAY` The singleton instance for the day-of-week of Sunday.
    `THURSDAY` The singleton instance for the day-of-week of Thursday.
    `TUESDAY` The singleton instance for the day-of-week of Tuesday.
    `WEDNESDAY` The singleton instance for the day-of-week of Wednesday.

  - ### 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 day-of-week.
    `static DayOfWeek` | `from(TemporalAccessor temporal)` Obtains an instance of `DayOfWeek` from a temporal object.
    `int` | `get(TemporalField field)` Gets the value of the specified field from this day-of-week as an `int`.
    `String` | `getDisplayName(TextStyle style, Locale locale)` Gets the textual representation, such as 'Mon' or 'Friday'.
    `long` | `getLong(TemporalField field)` Gets the value of the specified field from this day-of-week as a `long`.
    `int` | `getValue()` Gets the day-of-week `int` value.
    `boolean` | `isSupported(TemporalField field)` Checks if the specified field is supported.
    `DayOfWeek` | `minus(long days)` Returns the day-of-week that is the specified number of days before this one.
    `static DayOfWeek` | `of(int dayOfWeek)` Obtains an instance of `DayOfWeek` from an `int` value.
    `DayOfWeek` | `plus(long days)` Returns the day-of-week that is the specified number of days after this one.
    `<R> R` | `query(TemporalQuery<R> query)` Queries this day-of-week using the specified query.
    `ValueRange` | `range(TemporalField field)` Gets the range of valid values for the specified field.
    `static DayOfWeek` | `valueOf(String name)` Returns the enum constant of this type with the specified name.
    `static DayOfWeek[]` | `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

    - #### MONDAY

          public static final DayOfWeek MONDAY

      The singleton instance for the day-of-week of Monday. This has the numeric value of `1`.

    - #### TUESDAY

          public static final DayOfWeek TUESDAY

      The singleton instance for the day-of-week of Tuesday. This has the numeric value of `2`.

    - #### WEDNESDAY

          public static final DayOfWeek WEDNESDAY

      The singleton instance for the day-of-week of Wednesday. This has the numeric value of `3`.

    - #### THURSDAY

          public static final DayOfWeek THURSDAY

      The singleton instance for the day-of-week of Thursday. This has the numeric value of `4`.

    - #### FRIDAY

          public static final DayOfWeek FRIDAY

      The singleton instance for the day-of-week of Friday. This has the numeric value of `5`.

    - #### SATURDAY

          public static final DayOfWeek SATURDAY

      The singleton instance for the day-of-week of Saturday. This has the numeric value of `6`.

    - #### SUNDAY

          public static final DayOfWeek SUNDAY

      The singleton instance for the day-of-week of Sunday. This has the numeric value of `7`.

  - ### Method Detail

    - #### values

          public static DayOfWeek[] 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 (DayOfWeek c : DayOfWeek.values())
              System.out.println(c);

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

    - #### valueOf

          public static DayOfWeek 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 DayOfWeek of(int dayOfWeek)

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

      `DayOfWeek` is an enum representing the 7 days of the week. This factory allows the enum to be obtained from the `int` value. The `int` value follows the ISO-8601 standard, from 1 (Monday) to 7 (Sunday).

      Parameters:
        `dayOfWeek` - the day-of-week to represent, from 1 (Monday) to 7 (Sunday)
      Returns:
        the day-of-week singleton, not null
      Throws:
        `DateTimeException` - if the day-of-week is invalid

    - #### from

          public static DayOfWeek from(TemporalAccessor temporal)

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

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

      The conversion extracts the `DAY_OF_WEEK` field.

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

      Parameters:
        `temporal` - the temporal object to convert, not null
      Returns:
        the day-of-week, not null
      Throws:
        `DateTimeException` - if unable to convert to a `DayOfWeek`

    - #### getValue

          public int getValue()

      Gets the day-of-week `int` value.

      The values are numbered following the ISO-8601 standard, from 1 (Monday) to 7 (Sunday). See `WeekFields.dayOfWeek()` for localized week-numbering.

      Returns:
        the day-of-week, from 1 (Monday) to 7 (Sunday)

    - #### getDisplayName

          public String getDisplayName(TextStyle style,
                                       Locale locale)

      Gets the textual representation, such as 'Mon' or 'Friday'.

      This returns the textual name used to identify the day-of-week, 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 day-of-week, not null

    - #### isSupported

          public boolean isSupported(TemporalField field)

      Checks if the specified field is supported.

      This checks if this day-of-week can be queried for the specified field. If false, then calling the `range` and `get` methods will throw an exception.

      If the field is `DAY_OF_WEEK` 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 day-of-week, 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 day-of-week 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 `DAY_OF_WEEK` then the range of the day-of-week, from 1 to 7, 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 day-of-week as an `int`.

      This queries this day-of-week 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 `DAY_OF_WEEK` then the value of the day-of-week, from 1 to 7, 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 day-of-week as a `long`.

      This queries this day-of-week 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 `DAY_OF_WEEK` then the value of the day-of-week, from 1 to 7, 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 DayOfWeek plus(long days)

      Returns the day-of-week that is the specified number of days after this one.

      The calculation rolls around the end of the week from Sunday to Monday. The specified period may be negative.

      This instance is immutable and unaffected by this method call.

      Parameters:
        `days` - the days to add, positive or negative
      Returns:
        the resulting day-of-week, not null

    - #### minus

          public DayOfWeek minus(long days)

      Returns the day-of-week that is the specified number of days before this one.

      The calculation rolls around the start of the year from Monday to Sunday. The specified period may be negative.

      This instance is immutable and unaffected by this method call.

      Parameters:
        `days` - the days to subtract, positive or negative
      Returns:
        the resulting day-of-week, not null

    - #### query

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

      Queries this day-of-week using the specified query.

      This queries this day-of-week 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 day-of-week.

      This returns a temporal object of the same observable type as the input with the day-of-week changed to be the same as this.

      The adjustment is equivalent to using `Temporal.with(TemporalField, long)` passing `ChronoField.DAY_OF_WEEK` as the field. Note that this adjusts forwards or backwards within a Monday to Sunday week. See `WeekFields.dayOfWeek()` for localized week start days. See `TemporalAdjuster` for other adjusters with more control, such as `next(MONDAY)`.

      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 = thisDayOfWeek.adjustInto(temporal);
             temporal = temporal.with(thisDayOfWeek);

      For example, given a date that is a Wednesday, the following are output:

             dateOnWed.with(MONDAY);     // two days earlier
             dateOnWed.with(TUESDAY);    // one day earlier
             dateOnWed.with(WEDNESDAY);  // same date
             dateOnWed.with(THURSDAY);   // one day later
             dateOnWed.with(FRIDAY);     // two days later
             dateOnWed.with(SATURDAY);   // three days later
             dateOnWed.with(SUNDAY);     // four days 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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