org.apache.commons.rdf.api

Interface Literal

All Superinterfaces:

RDFTerm

All Known Subinterfaces:

JenaLiteral, JsonLdLiteral, RDF4JLiteral

public interface Literal
extends RDFTerm

An RDF-1.1 Literal, as defined by RDF-1.1 Concepts and Abstract Syntax, a W3C Recommendation published on 25 February 2014.

See Also:

RDF.createLiteral(String), RDF.createLiteral(String, IRI), RDF.createLiteral(String, String)

Method Summary

Modifier and Type	Method and Description
boolean	equals(Object other) Check it this Literal is equal to another Literal.
IRI	getDatatype() The IRI identifying the datatype that determines how the lexical form maps to a literal value.
Optional<String>	getLanguageTag() If and only if the datatype IRI is http://www.w3.org/1999/02/22-rdf-syntax-ns#langString, the language tag for this Literal is a non-empty language tag as defined by BCP47. If the datatype IRI is not http://www.w3.org/1999/02/22-rdf-syntax-ns#langString, this method must return Optional.empty().
String	getLexicalForm() The lexical form of this literal, represented by a Unicode string.
int	hashCode() Calculate a hash code for this Literal.

Methods inherited from interface org.apache.commons.rdf.api.RDFTerm

ntriplesString

Method Detail

getLexicalForm

String getLexicalForm()

The lexical form of this literal, represented by a Unicode string.

Returns:

The lexical form of this literal.

See Also:

RDF-1.1 Literal lexical form

getDatatype

IRI getDatatype()

The IRI identifying the datatype that determines how the lexical form maps to a literal value. If the datatype IRI is http://www.w3.org/1999/02/22-rdf-syntax-ns#langString, getLanguageTag() must not return Optional.empty(), and it must return a valid BCP47 language tag.

Returns:

The datatype IRI for this literal.

See Also:

RDF-1.1 Literal datatype IRI

getLanguageTag

Optional<String> getLanguageTag()

If and only if the datatype IRI is http://www.w3.org/1999/02/22-rdf-syntax-ns#langString, the language tag for this Literal is a non-empty language tag as defined by BCP47.
If the datatype IRI is not http://www.w3.org/1999/02/22-rdf-syntax-ns#langString, this method must return Optional.empty().

The value space of language tags is always in lower case; although RDF implementations MAY convert all language tags to lower case, safe comparisons of language tags should be done using String.toLowerCase(Locale) with the locale Locale.ROOT.

Implementation note: If your application requires Serializable objects, it is best not to store an Optional in a field. It is recommended to use Optional.ofNullable(Object) to create the return value for this method.

Returns:

The Optional language tag for this literal. If Optional.isPresent() returns true, the value returned by Optional.get() must be a non-empty language tag string conforming to BCP47.

See Also:

RDF-1.1 Literal language tag

equals

boolean equals(Object other)

Check it this Literal is equal to another Literal.

Literal term equality: Two literals are term-equal (the same RDF literal) if and only if the two lexical forms, the two datatype IRIs, and the two language tags (if any) compare equal, character by character. Thus, two literals can have the same value without being the same RDF term.

As the value space for language tags is lower-space, if they are present, they MUST be compared character by character using the equivalent of String.toLowerCase(java.util.Locale) with the locale Locale.ROOT.

Implementations MUST also override hashCode() so that two equal Literals produce the same hash code.

Specified by:

equals in interface RDFTerm

Overrides:

equals in class Object

Parameters:

other - Another object

Returns:

true if other is a Literal and is equal to this

See Also:

Object.equals(Object)

hashCode

int hashCode()

Calculate a hash code for this Literal.

The returned hash code MUST be equal to the result of Objects.hash(Object...) with the arguments getLexicalForm(), getDatatype(), getLanguageTag().map(s->s.toLowerString(Locale.ROOT)).

This method MUST be implemented in conjunction with equals(Object) so that two equal Literals produce the same hash code.

Specified by:

hashCode in interface RDFTerm

Overrides:

hashCode in class Object

Returns:

a hash code value for this Literal.

See Also:

Object.hashCode(), Objects.hash(Object...)