Module org.apache.sis.util
Package 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

If a character sequence given to the parse(Char­Sequence) method is of the form "EPSG:####", "urn:ogc:def:uom:EPSG::####" or "http://www​.opengis​.net/def/uom/EPSG/0/####" (ignoring case and whitespaces around path separators), then "####" is parsed as an integer and forwarded to the Units​.value­Of­EPSG(int) method.

Note on netCDF unit symbols

In netCDF files, values of "unit" attribute are concatenations of an angular unit with an axis direction, as in "degrees_east" or "degrees_north". This class ignores those suffixes and unconditionally returns Units​.DEGREE for all axis directions.

Multi-threading

Unit­Format is generally not thread-safe. If units need to be parsed or formatted in different threads, each thread should have its own Unit­Format instance.
Since:
0.8
See Also:

  • Constructor Details

    • 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 Details

    • 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:

    • 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. The set of legal characters may be expanded in future Apache SIS versions, but 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 cannot 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, or null if none.
      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 MeasurementParseException
      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”.

      This method differs from parse(Char­Sequence, Parse­Position) in the treatment of white spaces: that method with a Parse­Position argument stops parsing at the first white space, while this parse(…) method treats white spaces as multiplications. The reason for this difference is that white space is normally not a valid multiplication symbol; it could be followed by a text which is not part of the unit symbol. But in the case of this parse(Char­Sequence) method, the whole Char­Sequence shall be a unit symbol. In such case, white spaces are less ambiguous.

      The default implementation delegates to parse(symbols, new Parse­Position(0)) and verifies that all non-white characters have been parsed. Units separated by spaces are multiplied; for example "kg m**-2" is parsed as kg/m².

      Specified by:
      parse in interface Unit­Format
      Parameters:
      symbols - the unit symbols or URI to parse.
      Returns:
      the unit parsed from the specified symbols.
      Throws:
      Measurement­Parse­Exception - if a problem occurred while parsing the given symbols.
      See Also:

    • parse

      public Unit<?> parse(CharSequence symbols, ParsePosition position) throws MeasurementParseException
      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 Measurement­Parse­Exception is thrown.

      Specified by:
      parse in interface Unit­Format
      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:
      Measurement­Parse­Exception - 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 Measurement­Parse­Exception 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 cannot 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 Measurement­Parse­Exception.
      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.