How to use

concat

method

in

org.apache.jena.ext.com.google.common.collect.Iterators

/** Substitute into triple patterns */
public static Iterator<Triple> calcTriples(final List<Triple> triples, Iterator<Binding> bindings) {
  return Iterators.concat(Iter.map(bindings, new Function<Binding, Iterator<Triple>>() {
    Map<Node, Node> bNodeMap = new HashMap<>();
    @Override
    public Iterator<Triple> apply(final Binding b) {
      // Iteration is a new mapping of bnodes.
      bNodeMap.clear();
      List<Triple> tripleList = new ArrayList<>(triples.size());
      for ( Triple triple : triples ) {
        Triple q = subst(triple, b, bNodeMap);
        if ( !q.isConcrete() || !ModelUtils.isValidAsStatement(q.getSubject(), q.getPredicate(), q.getObject()) ) {
          // Log.warn(TemplateLib.class, "Unbound quad:
          // "+FmtUtils.stringForQuad(quad)) ;
          continue;
        }
        tripleList.add(q);
      }
      return tripleList.iterator();
    }
  }));
}

/** Substitute into quad patterns */
public static Iterator<Quad> calcQuads(final List<Quad> quads, Iterator<Binding> bindings) {
  return Iterators.concat(Iter.map(bindings, new Function<Binding, Iterator<Quad>>() {
    Map<Node, Node> bNodeMap = new HashMap<>();
    @Override
    public Iterator<Quad> apply(final Binding b) {
      // Iteration is a new mapping of bnodes.
      bNodeMap.clear();
      List<Quad> quadList = new ArrayList<>(quads.size());
      for ( Quad quad : quads ) {
        Quad q = subst(quad, b, bNodeMap);
        if ( !q.isConcrete() ) {
          // Log.warn(TemplateLib.class, "Unbound quad:
          // "+FmtUtils.stringForQuad(quad)) ;
          continue;
        }
        quadList.add(q);
      }
      return quadList.iterator();
    }
  }));
}

@Override
public Iterator<Quad> find(Node g, Node s, Node p, Node o) {
  return g.isConcrete()
      ? findInOneGraph(g, s, p, o)
      : concat(findNG(ANY, s, p, o), findInOneGraph(defaultGraphIRI, s, p, o));
}

@Override
public Iterator<Quad> findNG(Node g, Node s, Node p, Node o) {
  return g.isConcrete()
      ? findInOneGraph(g, s, p, o)
      : concat(map(listGraphNodes(), gn -> findInOneGraph(gn, s, p, o)));
}