org.apache.sis.measure

## Class UnitFormat

- Object
- - Format
  - - UnitFormat

- All Implemented Interfaces:
    Serializable, Cloneable, UnitFormat, Localized

      public class UnitFormat
      extends Format
      implements UnitFormat, Localized

  Parses and formats units of measurement as SI symbols, URI in OGC namespace or other symbols. This class combines in a single class the API from `java​.text` and the API from `javax​.measure​.format`. In addition to the symbols of the Système international (SI), this class is also capable to handle some symbols found in Well Known Text (WKT) definitions or in XML files.
  Parsing authority codes
  As a special case, if a character sequence given to the `parse(CharSequence)` method is of the `"EPSG:####"` or `"urn:ogc:def:uom:EPSG::####"` form (ignoring case and whitespaces), then `"####"` is parsed as an integer and forwarded to the `Units​.valueOfEPSG(int)` method.
  NetCDF unit symbols
  The attributes in netCDF files often merge the axis direction with the angular unit, as in `"degrees_east"`, `"degrees_north"` or `"Degrees North"`. This class ignores those suffixes and unconditionally returns `Units​.DEGREE` for all axis directions. In particular, the units for `"degrees_west"` and `"degrees_east"` do not have opposite sign. It is caller responsibility to handle the direction of axes associated to netCDF units.
  Multi-threading
  `UnitFormat` is generally not thread-safe. However if there is no call to any setter method or to `label(Unit, String)` after construction, then the `parse(CharSequence)` and `format(Unit)` methods can be invoked concurrently in different threads.
  Since:
    0.8
  See Also:
    `Units​.valueOf(String)`, Serialized Form

  Defined in the `sis-utility` module

- - ### Nested Class Summary

    Nested Classes
    Modifier and Type | Class and Description
    --- | ---
    `static class` | `UnitFormat.Style` Identify whether unit formatting uses ASCII symbols, Unicode symbols or full localized names.

    - ### Nested classes/interfaces inherited from class Format

      `Format​.Field`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `UnitFormat(Locale locale)` Creates a new format for the given locale.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `UnitFormat` | `clone()` Returns a clone of this unit format.
    `StringBuffer` | `format(Object unit, StringBuffer toAppendTo, FieldPosition pos)` Formats the specified unit in the given buffer.
    `String` | `format(Unit<?> unit)` Formats the given unit.
    `Appendable` | `format(Unit<?> unit, Appendable toAppendTo)` Formats the specified unit.
    `Locale` | `getLocale()` Returns the locale used by this `UnitFormat`.
    `UnitFormat.Style` | `getStyle()` Returns whether unit formatting uses ASCII symbols, Unicode symbols or full localized names.
    `boolean` | `isLocaleSensitive()` Returns whether this `UnitFormat` depends on the `Locale` given at construction time for performing its tasks.
    `void` | `label(Unit<?> unit, String label)` Attaches a label to the specified unit.
    `Unit<?>` | `parse(CharSequence symbols)` Parses the given text as an instance of `Unit`.
    `Unit<?>` | `parse(CharSequence symbols, ParsePosition position)` Parses a portion of the given text as an instance of `Unit`.
    `Object` | `parseObject(String source)` Parses text from a string to produce a unit.
    `Object` | `parseObject(String source, ParsePosition pos)` Parses text from a string to produce a unit, or returns `null` if the parsing failed.
    `void` | `setLocale(Locale locale)` Sets the locale that this `UnitFormat` will use for long names.
    `void` | `setStyle(UnitFormat.Style style)` Sets whether unit formatting should use ASCII symbols, Unicode symbols or full localized names.

    - ### Methods inherited from class Format

      `format, formatToCharacterIterator`

    - ### Methods inherited from class Object

      `equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Constructor Detail

    - #### UnitFormat

          public UnitFormat(Locale locale)

      Creates a new format for the given locale.
      Parameters:
        `locale` - the locale to use for parsing and formatting units.

  - ### Method Detail

    - #### getLocale

          public Locale getLocale()

      Returns the locale used by this `UnitFormat`.
      Specified by:
        `getLocale` in interface `Localized`
      Returns:
        the locale of this `UnitFormat`.

    - #### setLocale

          public void setLocale(Locale locale)

      Sets the locale that this `UnitFormat` will use for long names. For example a call to `setLocale(Locale​.US)` instructs this formatter to use the “meter” spelling instead of “metre”.
      Parameters:
        `locale` - the new locale for this `UnitFormat`.
      See Also:
        `UnitServices​.getUnitFormat(String)`

    - #### isLocaleSensitive

          public boolean isLocaleSensitive()

      Returns whether this `UnitFormat` depends on the `Locale` given at construction time for performing its tasks. This method returns `true` if formatting long names (e.g. “metre” or “meter”} and `false` if formatting only the unit symbol (e.g. “m”).
      Specified by:
        `isLocaleSensitive` in interface `UnitFormat`
      Returns:
        `true` if formatting depends on the locale.

    - #### getStyle

          public UnitFormat.Style getStyle()

      Returns whether unit formatting uses ASCII symbols, Unicode symbols or full localized names.
      Returns:
        the style of units formatted by this `UnitFormat` instance.

    - #### setStyle

          public void setStyle(UnitFormat.Style style)

      Sets whether unit formatting should use ASCII symbols, Unicode symbols or full localized names.
      Parameters:
        `style` - the desired style of units.

    - #### label

          public void label(Unit<?> unit,
                            String label)

      Attaches a label to the specified unit. A label can be a substitute to either the unit symbol or the `unit name`, depending on the format style. If the specified label is already associated to another unit, then the previous association is discarded.
      Restriction on character set
      Current implementation accepts only letters, subscripts, spaces (including non-breaking spaces but not CR/LF characters), the degree sign (°) and a few other characters like underscore, but the set of legal characters may be expanded in future Apache SIS versions. However the following restrictions are likely to remain:
      - The following characters are reserved since they have special meaning in UCUM format, in URI or in Apache SIS parser:

        > " # ( ) * + - . / : = ? [ ] { } ^ ⋅ ∕

      - The symbol can not begin or end with digits, since such digits would be confused with unit power.
      Specified by:
        `label` in interface `UnitFormat`
      Parameters:
        `unit` - the unit being labeled.
        `label` - the new label for the given unit.
      Throws:
        `IllegalArgumentException` - if the given label is not a valid unit name.

    - #### format

          public Appendable format(Unit<?> unit,
                                   Appendable toAppendTo)
                            throws IOException

      Formats the specified unit. This method performs the first of the following actions that can be done.
      1. If a label has been specified for the given unit, then that label is appended unconditionally.
      2. Otherwise if the formatting style is `UnitFormat​.Style​.NAME` and the `Unit​.getName()` method returns a non-null value, then that value is appended. `Unit` instances implemented by Apache SIS are handled in a special way for localizing the name according the locale specified to this format.
      3. Otherwise if the `Unit​.getSymbol()` method returns a non-null value, then that value is appended.
      4. Otherwise a default symbol is created from the entries returned by `Unit​.getBaseUnits()`.
      Specified by:
        `format` in interface `UnitFormat`
      Parameters:
        `unit` - the unit to format.
        `toAppendTo` - where to format the unit.
      Returns:
        the given `toAppendTo` argument, for method calls chaining.
      Throws:
        `IOException` - if an error occurred while writing to the destination.

    - #### format

          public StringBuffer format(Object unit,
                                     StringBuffer toAppendTo,
                                     FieldPosition pos)

      Formats the specified unit in the given buffer. This method delegates to `format(Unit, Appendable)`.
      Specified by:
        `format` in class `Format`
      Parameters:
        `unit` - the unit to format.
        `toAppendTo` - where to format the unit.
        `pos` - where to store the position of a formatted field.
      Returns:
        the given `toAppendTo` argument, for method calls chaining.

    - #### format

          public String format(Unit<?> unit)

      Formats the given unit. This method delegates to `format(Unit, Appendable)`.
      Specified by:
        `format` in interface `UnitFormat`
      Parameters:
        `unit` - the unit to format.
      Returns:
        the formatted unit.

    - #### parse

          public Unit<?> parse(CharSequence symbols)
                        throws ParserException

      Parses the given text as an instance of `Unit`. If the parse completes without reading the entire length of the text, an exception is thrown.

      The parsing is lenient: symbols can be products or quotients of units like “m∕s”, words like “meters per second”, or authority codes like `"urn:ogc:def:uom:EPSG::1026"`. The product operator can be either `'.'` (ASCII) or `'⋅'` (Unicode) character. Exponent after symbol can be decimal digits as in “m2” or a superscript as in “m²”.

      The default implementation delegates to `parse(symbols, new ParsePosition(0))` and verifies that all non-white characters have been parsed.

      Specified by:
        `parse` in interface `UnitFormat`
      Parameters:
        `symbols` - the unit symbols or URI to parse.
      Returns:
        the unit parsed from the specified symbols.
      Throws:
        `ParserException` - if a problem occurred while parsing the given symbols.
      See Also:
        `Units​.valueOf(String)`

    - #### parse

          public Unit<?> parse(CharSequence symbols,
                               ParsePosition position)
                        throws ParserException

      Parses a portion of the given text as an instance of `Unit`. Parsing begins at the index given by `ParsePosition​.getIndex()`. After parsing, the above-cited index is updated to the first unparsed character.

      The parsing is lenient: symbols can be products or quotients of units like “m∕s”, words like “meters per second”, or authority codes like `"urn:ogc:def:uom:EPSG::1026"`. The product operator can be either `'.'` (ASCII) or `'⋅'` (Unicode) character. Exponent after symbol can be decimal digits as in “m2” or a superscript as in “m²”.

      Note that contrarily to `parseObject(String, ParsePosition)`, this method never return `null`. If an error occurs at parsing time, an unchecked `ParserException` is thrown.

      Parameters:
        `symbols` - the unit symbols to parse.
        `position` - on input, index of the first character to parse. On output, index after the last parsed character.
      Returns:
        the unit parsed from the specified symbols.
      Throws:
        `ParserException` - if a problem occurred while parsing the given symbols.

    - #### parseObject

          public Object parseObject(String source)
                             throws ParseException

      Parses text from a string to produce a unit. The default implementation delegates to `parse(CharSequence)` and wraps the `ParserException` into a `ParseException` for compatibility with `java​.text` API.
      Overrides:
        `parseObject` in class `Format`
      Parameters:
        `source` - the text, part of which should be parsed.
      Returns:
        a unit parsed from the string.
      Throws:
        `ParseException` - if the given string can not be fully parsed.

    - #### parseObject

          public Object parseObject(String source,
                                    ParsePosition pos)

      Parses text from a string to produce a unit, or returns `null` if the parsing failed. The default implementation delegates to `parse(CharSequence, ParsePosition)` and catches the `ParserException`.
      Specified by:
        `parseObject` in class `Format`
      Parameters:
        `source` - the text, part of which should be parsed.
        `pos` - index and error index information as described above.
      Returns:
        a unit parsed from the string, or `null` in case of error.

    - #### clone

          public UnitFormat clone()

      Returns a clone of this unit format. The new unit format will be initialized to the same locale and labels than this format.
      Overrides:
        `clone` in class `Format`
      Returns:
        a clone of this unit format.

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