org.apache.sis.referencing.datum

## Class AbstractDatum

- Object
- - FormattableObject
  - - AbstractIdentifiedObject
    - - AbstractDatum

- All Implemented Interfaces:
    Serializable, Deprecable, LenientComparable, Datum, IdentifiedObject
  Direct Known Subclasses:
    DefaultEngineeringDatum, DefaultGeodeticDatum, DefaultImageDatum, DefaultParametricDatum, DefaultTemporalDatum, DefaultVerticalDatum

      public class AbstractDatum
      extends AbstractIdentifiedObject
      implements Datum

  Specifies the relationship of a Coordinate System to the earth. A datum can be defined as a set of real points on the earth that have coordinates. Each datum subtype can be associated with only specific types of coordinate systems, thus creating specific types of coordinate reference system.
  Instantiation
  This class is conceptually abstract, even if it is technically possible to instantiate it. Typical applications should create instances of the most specific subclass prefixed by `Default` instead.
  Immutability and thread safety
  This base class is immutable if the property values (not necessarily the map itself) given to the constructor are also immutable. Most SIS subclasses and related classes are immutable under similar conditions. This means that unless otherwise noted in the javadoc, `Datum` instances created using only SIS factories and static constants can be shared by many objects and passed between threads without synchronization.
  Since:
    0.4
  See Also:
    `AbstractCS`, `AbstractCRS`, Serialized Form

  Defined in the `sis-referencing` module

- - ### Field Summary

    - ### Fields inherited from class AbstractIdentifiedObject

      `DEPRECATED_KEY, LOCALE_KEY`

    - ### Fields inherited from interface Datum

      `ANCHOR_POINT_KEY, DOMAIN_OF_VALIDITY_KEY, REALIZATION_EPOCH_KEY, SCOPE_KEY`

    - ### Fields inherited from interface IdentifiedObject

      `ALIAS_KEY, IDENTIFIERS_KEY, NAME_KEY, REMARKS_KEY`

  - ### Constructor Summary

    Constructors
    Modifier | Constructor and Description
    --- | ---
    `protected` | `AbstractDatum(Datum datum)` Creates a new datum with the same values than the specified one.
    `` | `AbstractDatum(Map<String,?> properties)` Creates a datum from the given properties.

  - ### Method Summary

    All Methods Static Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `static AbstractDatum` | `castOrCopy(Datum object)` Returns a SIS datum implementation with the values of the given arbitrary implementation.
    `protected long` | `computeHashCode()` Invoked by `hashCode()` for computing the hash code when first needed.
    `boolean` | `equals(Object object, ComparisonMode mode)` Compares the specified object with this datum for equality.
    `protected String` | `formatTo(Formatter formatter)` Formats the inner part of the Well Known Text (WKT) representation for this datum.
    `InternationalString` | `getAnchorPoint()` Returns a description of the point(s) used to anchor the datum to the Earth.
    `Extent` | `getDomainOfValidity()` Returns the region or timeframe in which this datum is valid, or `null` if unspecified.
    `Class<? extends Datum>` | `getInterface()` Returns the GeoAPI interface implemented by this class.
    `Date` | `getRealizationEpoch()` The time after which this datum definition is valid.
    `InternationalString` | `getScope()` Returns the domain or limitations of usage, or `null` if unspecified.
    `boolean` | `isHeuristicMatchForName(String name)` Returns `true` if either the primary name or at least one alias matches the given string according heuristic rules.

    - ### Methods inherited from class AbstractIdentifiedObject

      `castOrCopy, equals, getAlias, getDescription, getIdentifiers, getName, getRemarks, hashCode, isDeprecated`

    - ### Methods inherited from class FormattableObject

      `print, toString, toString, toWKT`

    - ### Methods inherited from class Object

      `clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

    - ### Methods inherited from interface IdentifiedObject

      `getAlias, getIdentifiers, getName, getRemarks, toWKT`

- - ### Constructor Detail

    - #### AbstractDatum

          public AbstractDatum(Map<String,?> properties)

      Creates a datum from the given properties. The properties given in argument follow the same rules than for the super-class constructor. Additionally, the following properties are understood by this constructor:

      Recognized properties (non exhaustive list)
      Property name | Value type | Returned by
      --- | --- | ---
      "anchorPoint" | `InternationalString` or `String` | `getAnchorPoint()`
      "realizationEpoch" | `Date` | `getRealizationEpoch()`
      "domainOfValidity" | `Extent` | `getDomainOfValidity()`
      "scope" | `InternationalString` or `String` | `getScope()`
      Defined in parent class (reminder)
      "name" | `ReferenceIdentifier` or `String` | `AbstractIdentifiedObject.getName()`
      "alias" | `GenericName` or `CharSequence` (optionally as array) | `AbstractIdentifiedObject.getAlias()`
      "identifiers" | `ReferenceIdentifier` (optionally as array) | `AbstractIdentifiedObject.getIdentifiers()`
      "remarks" | `InternationalString` or `String` | `AbstractIdentifiedObject.getRemarks()`

      Parameters:
        `properties` - the properties to be given to the identified object.

    - #### AbstractDatum

          protected AbstractDatum(Datum datum)

      Creates a new datum with the same values than the specified one. This copy constructor provides a way to convert an arbitrary implementation into a SIS one or a user-defined one (as a subclass), usually in order to leverage some implementation-specific API.

      This constructor performs a shallow copy, i.e. the properties are not cloned.

      Parameters:
        `datum` - the datum to copy.

  - ### Method Detail

    - #### castOrCopy

          public static AbstractDatum castOrCopy(Datum object)

      Returns a SIS datum implementation with the values of the given arbitrary implementation. This method performs the first applicable action in the following choices:
      - If the given object is `null`, then this method returns `null`.
      - Otherwise if the given object is an instance of `GeodeticDatum`, `VerticalDatum`, `TemporalDatum`, `EngineeringDatum` or `ImageDatum`, then this method delegates to the `castOrCopy(…)` method of the corresponding SIS subclass. Note that if the given object implements more than one of the above-cited interfaces, then the `castOrCopy(…)` method to be used is unspecified.
      - Otherwise if the given object is already an instance of `AbstractDatum`, then it is returned unchanged.
      - Otherwise a new `AbstractDatum` instance is created using the copy constructor and returned. Note that this is a shallow copy operation, since the other properties contained in the given object are not recursively copied.
      Parameters:
        `object` - the object to get as a SIS implementation, or `null` if none.
      Returns:
        a SIS implementation containing the values of the given object (may be the given object itself), or `null` if the argument was null.

    - #### getInterface

          public Class<? extends Datum> getInterface()

      Returns the GeoAPI interface implemented by this class. The default implementation returns `Datum​.class`. Subclasses implementing a more specific GeoAPI interface shall override this method.
      Overrides:
        `getInterface` in class `AbstractIdentifiedObject`
      Returns:
        the datum interface implemented by this class.

    - #### getAnchorPoint

          public InternationalString getAnchorPoint()

      Returns a description of the point(s) used to anchor the datum to the Earth. Also known as the "origin", especially for Engineering and Image Datums.
      - For a geodetic datum, the anchor may be the point(s) where the relationship between geoid and ellipsoid is defined.
      - For an engineering datum, the anchor may be an identified physical point with the orientation defined relative to the object.
      - For an image datum, the anchor point may be the centre or the corner of the image.
      - For a temporal datum, see their origin instead.
      Specified by:
        `getAnchorPoint` in interface `Datum`
      Returns:
        description, possibly including coordinates, of the point or points used to anchor the datum to the Earth.

    - #### getRealizationEpoch

          public Date getRealizationEpoch()

      The time after which this datum definition is valid. This time may be precise or merely a year.

      If an old datum is superseded by a new datum, then the realization epoch for the new datum defines the upper limit for the validity of the old datum.

      Specified by:
        `getRealizationEpoch` in interface `Datum`
      Returns:
        the time after which this datum definition is valid, or `null` if none.

    - #### getDomainOfValidity

          public Extent getDomainOfValidity()

      Returns the region or timeframe in which this datum is valid, or `null` if unspecified.
      Specified by:
        `getDomainOfValidity` in interface `Datum`
      Returns:
        area or region or timeframe in which this datum is valid, or `null`.
      See Also:
        `DefaultExtent`

    - #### getScope

          public InternationalString getScope()

      Returns the domain or limitations of usage, or `null` if unspecified.
      Specified by:
        `getScope` in interface `Datum`
      Returns:
        description of domain of usage, or limitations of usage, for which this datum object is valid.

    - #### isHeuristicMatchForName

          public boolean isHeuristicMatchForName(String name)

      Returns `true` if either the primary name or at least one alias matches the given string according heuristic rules. This method performs the comparison documented in the super-class, with the following additional flexibility:
      - The `"D_"` prefix (used in ESRI datum names), if presents in the given name or in this datum name, is ignored.
      - If this datum is an instance of `DefaultGeodeticDatum`, then the prime meridian name may also be ignored.
      Future evolutions
      This method implements heuristic rules learned from experience while trying to provide inter-operability with different data producers. Those rules may be adjusted in any future SIS version according experience gained while working with more data producers.
      Overrides:
        `isHeuristicMatchForName` in class `AbstractIdentifiedObject`
      Parameters:
        `name` - the name to compare.
      Returns:
        `true` if the primary name or at least one alias matches the specified `name`.
      See Also:
        `IdentifiedObjects​.isHeuristicMatchForName(IdentifiedObject, String)`, `Characters​.Filter​.LETTERS_AND_DIGITS`

    - #### equals

          public boolean equals(Object object,
                                ComparisonMode mode)

      Compares the specified object with this datum for equality. If the `mode` argument value is `STRICT` or `BY_CONTRACT`, then all available properties are compared including the anchor point, realization epoch, domain of validity and the scope.
      Specified by:
        `equals` in interface `LenientComparable`
      Overrides:
        `equals` in class `AbstractIdentifiedObject`
      Parameters:
        `object` - the object to compare to `this`.
        `mode` - `STRICT` for performing a strict comparison, or `IGNORE_METADATA` for comparing only properties relevant to coordinate transformations.
      Returns:
        `true` if both objects are equal.
      See Also:
        `AbstractIdentifiedObject​.computeHashCode()`, `Utilities​.deepEquals(Object, Object, ComparisonMode)`

    - #### computeHashCode

          protected long computeHashCode()

      Invoked by `hashCode()` for computing the hash code when first needed. See `AbstractIdentifiedObject​.computeHashCode()` for more information.
      Overrides:
        `computeHashCode` in class `AbstractIdentifiedObject`
      Returns:
        the hash code value. This value may change in any future Apache SIS version.

    - #### formatTo

          protected String formatTo(Formatter formatter)

      Formats the inner part of the Well Known Text (WKT) representation for this datum. See `AbstractIdentifiedObject​.formatTo(Formatter)` for more information.
      Overrides:
        `formatTo` in class `AbstractIdentifiedObject`
      Parameters:
        `formatter` - the formatter where to format the inner content of this WKT element.
      Returns:
        the CamelCase keyword for the WKT element, or `null` if unknown.
      See Also:
        WKT 2 specification §7

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