Example usage for org.apache.commons.rdf.api Graph iterate

Introduction

In this page you can find the example usage for org.apache.commons.rdf.api Graph iterate.

Prototype

@SuppressWarnings("unchecked")
default Iterable<Triple> iterate(BlankNodeOrIRI subject, IRI predicate, RDFTerm object)
        throws ConcurrentModificationException, IllegalStateException 

Source Link

Document

Get an Iterable for iterating over the triples in the graph that match the pattern.

Usage

From source file:example.IntroToRDF.java

public static void main(String[] args) {
    RDF rdf = new SimpleRDF();

    IRI alice = rdf.createIRI("Alice");
    System.out.println(alice.ntriplesString());

    IRI knows = rdf.createIRI("knows");
    IRI bob = rdf.createIRI("Bob");

    Triple aliceKnowsBob = rdf.createTriple(alice, knows, bob);
    System.out.println(aliceKnowsBob.getSubject().ntriplesString());

    System.out.println(aliceKnowsBob);

    Graph graph = rdf.createGraph();
    graph.add(aliceKnowsBob);/*from  ww w.j  a  v a2  s  .  com*/

    IRI charlie = rdf.createIRI("Charlie");

    IRI plays = rdf.createIRI("plays");

    IRI football = rdf.createIRI("Football");
    IRI tennis = rdf.createIRI("Tennis");

    graph.add(alice, knows, charlie);
    graph.add(alice, plays, tennis);
    graph.add(bob, knows, charlie);
    graph.add(bob, plays, football);
    graph.add(charlie, plays, tennis);

    System.out.println("Who plays Tennis?");
    for (Triple triple : graph.iterate(null, plays, tennis)) {
        System.out.println(triple.getSubject());
        System.out.println(plays.equals(triple.getPredicate()));
        System.out.println(tennis.equals(triple.getObject()));
    }

    System.out.println("Who does Alice know?");
    for (Triple triple : graph.iterate(alice, knows, null)) {
        System.out.println(triple.getObject());
    }

    System.out.println("Does Alice anyone that plays Football?");
    for (Triple triple : graph.iterate(alice, knows, null)) {
        RDFTerm aliceFriend = triple.getObject();
        if (!(aliceFriend instanceof BlankNodeOrIRI)) {
            continue;
        }
        if (graph.contains((BlankNodeOrIRI) aliceFriend, plays, football)) {
            System.out.println("Yes, it is " + aliceFriend);
        }
    }

    Literal aliceName = rdf.createLiteral("Alice W. Land");
    IRI name = rdf.createIRI("name");
    graph.add(alice, name, aliceName);

    Optional<? extends Triple> nameTriple = graph.stream(alice, name, null).findAny();
    if (nameTriple.isPresent()) {
        System.out.println(nameTriple.get());
    }

    graph.stream(alice, name, null).findAny().map(Triple::getObject).filter(obj -> obj instanceof Literal)
            .map(literalName -> ((Literal) literalName).getLexicalForm()).ifPresent(System.out::println);

    IRI playerRating = rdf.createIRI("playerRating");
    Literal aliceRating = rdf.createLiteral("13.37", Types.XSD_FLOAT);
    graph.add(alice, playerRating, aliceRating);

    Literal footballInEnglish = rdf.createLiteral("football", "en");
    Literal footballInNorwegian = rdf.createLiteral("fotball", "no");
    graph.add(football, name, footballInEnglish);
    graph.add(football, name, footballInNorwegian);

    Literal footballInAmericanEnglish = rdf.createLiteral("soccer", "en-US");
    graph.add(football, name, footballInAmericanEnglish);

    BlankNode someone = rdf.createBlankNode();
    graph.add(charlie, knows, someone);
    graph.add(someone, plays, football);

    BlankNode someoneElse = rdf.createBlankNode();
    graph.add(charlie, knows, someoneElse);

    for (Triple heKnows : graph.iterate(charlie, knows, null)) {
        if (!(heKnows.getObject() instanceof BlankNodeOrIRI)) {
            continue;
        }
        BlankNodeOrIRI who = (BlankNodeOrIRI) heKnows.getObject();
        System.out.println("Charlie knows " + who);
        for (Triple whoPlays : graph.iterate(who, plays, null)) {
            System.out.println("  who plays " + whoPlays.getObject());
        }
    }

    // Delete previous BlankNode statements
    graph.remove(null, null, someone);
    graph.remove(someone, null, null);

    // no Java variable for the new BlankNode instance
    graph.add(charlie, knows, rdf.createBlankNode("someone"));
    // at any point later (with the same RDF instance)
    graph.add(rdf.createBlankNode("someone"), plays, football);

    for (Triple heKnows : graph.iterate(charlie, knows, null)) {
        if (!(heKnows.getObject() instanceof BlankNodeOrIRI)) {
            continue;
        }
        BlankNodeOrIRI who = (BlankNodeOrIRI) heKnows.getObject();
        System.out.println("Charlie knows " + who);
        for (Triple whoPlays : graph.iterate(who, plays, null)) {
            System.out.println("  who plays " + whoPlays.getObject());
        }
    }

}

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