Example usage for com.google.common.collect Iterators advance

Introduction

In this page you can find the example usage for com.google.common.collect Iterators advance.

Prototype

public static int advance(Iterator<?> iterator, int numberToAdvance) 

Source Link

Document

Calls next() on iterator , either numberToAdvance times or until hasNext() returns false , whichever comes first.

Usage

From source file:org.apache.marmotta.commons.sesame.repository.ResourceUtils.java

/**
 * List resources with the given prefix/*w  w  w .j  a v a 2 s .co m*/
 *
 * @param prefix the prefix
 * @param offset
 * @param limit
 */
public static Iterable<URI> listResourcesByPrefix(final RepositoryConnection con, final String prefix,
        final int offset, final int limit) {
    final ResourceConnection rcon = getWrappedResourceConnection(con);

    if (rcon != null) {
        return new Iterable<URI>() {
            @Override
            public Iterator<URI> iterator() {
                try {
                    Iterator<URI> result = ResultUtils.unwrap(rcon.getResources(prefix));

                    Iterators.advance(result, offset);

                    if (limit > 0) {
                        return Iterators.limit(result, limit);
                    } else {
                        return result;
                    }
                } catch (RepositoryException e) {
                    ExceptionUtils.handleRepositoryException(e, ResourceUtils.class);
                    return Iterators.emptyIterator();
                }

            }
        };
    } else {
        // no direct prefix listing support, need to filter the listResources result
        return new Iterable<URI>() {
            @Override
            public Iterator<URI> iterator() {
                Iterator<URI> result = Iterators
                        .transform(Iterators.filter(listResources(con).iterator(), new Predicate<Resource>() {
                            @Override
                            public boolean apply(Resource input) {
                                return input instanceof URI && input.stringValue().startsWith(prefix);
                            }
                        }), new Function<Resource, URI>() {
                            @Override
                            public URI apply(Resource input) {
                                return (URI) input;
                            }
                        });

                Iterators.advance(result, offset);

                if (limit > 0) {
                    return Iterators.limit(result, limit);
                } else {
                    return result;
                }
            }
        };
    }
}

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From source file:org.locationtech.geogig.geotools.data.reader.FeatureReaderBuilder.java

private <T> AutoCloseableIterator<T> applyOffsetAndLimit(AutoCloseableIterator<T> iterator) {
    Integer offset = this.offset;
    Integer limit = this.limit;
    if (offset != null) {
        Iterators.advance(iterator, offset.intValue());
    }/*from  w  w w. j ava  2s .c  o m*/
    if (limit != null) {
        iterator = AutoCloseableIterator.limit(iterator, limit.intValue());
    }
    return iterator;
}

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From source file:org.locationtech.geogig.web.api.ResponseWriter.java

/**
 * Writes the response for a set of diffs while also supplying the geometry.
 * //ww  w. java  2  s  .co  m
 * @param geogig - a CommandLocator to call commands from
 * @param diff - a DiffEntry iterator to build the response from
 * @throws XMLStreamException
 */
public void writeGeometryChanges(final Context geogig, Iterator<DiffEntry> diff, int page, int elementsPerPage)
        throws XMLStreamException {

    Iterators.advance(diff, page * elementsPerPage);
    int counter = 0;

    Iterator<GeometryChange> changeIterator = Iterators.transform(diff,
            new Function<DiffEntry, GeometryChange>() {
                @Override
                public GeometryChange apply(DiffEntry input) {
                    Optional<RevObject> feature = Optional.absent();
                    Optional<RevObject> type = Optional.absent();
                    String path = null;
                    String crsCode = null;
                    GeometryChange change = null;
                    if (input.changeType() == ChangeType.ADDED || input.changeType() == ChangeType.MODIFIED) {
                        feature = geogig.command(RevObjectParse.class).setObjectId(input.newObjectId()).call();
                        type = geogig.command(RevObjectParse.class)
                                .setObjectId(input.getNewObject().getMetadataId()).call();
                        path = input.getNewObject().path();

                    } else if (input.changeType() == ChangeType.REMOVED) {
                        feature = geogig.command(RevObjectParse.class).setObjectId(input.oldObjectId()).call();
                        type = geogig.command(RevObjectParse.class)
                                .setObjectId(input.getOldObject().getMetadataId()).call();
                        path = input.getOldObject().path();
                    }
                    if (feature.isPresent() && feature.get() instanceof RevFeature && type.isPresent()
                            && type.get() instanceof RevFeatureType) {
                        RevFeatureType featureType = (RevFeatureType) type.get();
                        Collection<PropertyDescriptor> attribs = featureType.type().getDescriptors();

                        for (PropertyDescriptor attrib : attribs) {
                            PropertyType attrType = attrib.getType();
                            if (attrType instanceof GeometryType) {
                                GeometryType gt = (GeometryType) attrType;
                                CoordinateReferenceSystem crs = gt.getCoordinateReferenceSystem();
                                if (crs != null) {
                                    try {
                                        crsCode = CRS.lookupIdentifier(Citations.EPSG, crs, false);
                                    } catch (FactoryException e) {
                                        crsCode = null;
                                    }
                                    if (crsCode != null) {
                                        crsCode = "EPSG:" + crsCode;
                                    }
                                }
                                break;
                            }
                        }

                        RevFeature revFeature = (RevFeature) feature.get();
                        FeatureBuilder builder = new FeatureBuilder(featureType);
                        GeogigSimpleFeature simpleFeature = (GeogigSimpleFeature) builder
                                .build(revFeature.getId().toString(), revFeature);
                        change = new GeometryChange(simpleFeature, input.changeType(), path, crsCode);
                    }
                    return change;
                }
            });

    while (changeIterator.hasNext() && (elementsPerPage == 0 || counter < elementsPerPage)) {
        GeometryChange next = changeIterator.next();
        if (next != null) {
            GeogigSimpleFeature feature = next.getFeature();
            ChangeType change = next.getChangeType();
            out.writeStartElement("Feature");
            writeElement("change", change.toString());
            writeElement("id", next.getPath());
            List<Object> attributes = feature.getAttributes();
            for (Object attribute : attributes) {
                if (attribute instanceof Geometry) {
                    writeElement("geometry", ((Geometry) attribute).toText());
                    break;
                }
            }
            if (next.getCRS() != null) {
                writeElement("crs", next.getCRS());
            }
            out.writeEndElement();
            counter++;
        }
    }
    if (changeIterator.hasNext()) {
        writeElement("nextPage", "true");
    }
}

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