private final Stats yStats;
  private final double sumOfProductsOfDeltas;

  /**
   * Internal constructor. Users should use {@link PairedStatsAccumulator#snapshot}.
   *
   * <p>To ensure that the created instance obeys its contract, the parameters should satisfy the
   * following constraints. This is the callers responsibility and is not enforced here.
   *
   * <ul>

   */
  public static Function<Object, String> toStringFunction() {
    return ToStringFunction.INSTANCE;
  }

  // enum singleton pattern
  private enum ToStringFunction implements Function<Object, String> {
    INSTANCE;

    @Override
    public String apply(Object o) {
      checkNotNull(o); // eager for GWT.
      return o.toString();
    }

    @Override

   * float[])}.
   *
   * @since 2.0
   */
  public static Comparator<float[]> lexicographicalComparator() {
    return LexicographicalComparator.INSTANCE;
  }

  private enum LexicographicalComparator implements Comparator<float[]> {
    INSTANCE;

    @Override
    public int compare(float[] left, float[] right) {
      int minLength = Math.min(left.length, right.length);

specific language governing permissions and limitations
under the License.
-->

<paramdoc xmlns="http://maven.apache.org/POM/4.0.0"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 ../../../../../../../maven-plugin-parameter-documenter/target/generated-site/xsd/paramdoc-1.0.0.xsd ">
  <expressions>
    <expression>

 * finalize statistics collection.
 *
 */
public class CrawlerStatsHelper {

    /**
     * Creates a new instance of CrawlerStatsHelper.
     */
    public CrawlerStatsHelper() {
        // Default constructor
    }

    /** Logger instance for this class. */
    private static final Logger logger = LogManager.getLogger(CrawlerStatsHelper.class);

 *   <li>Old document deletion after successful crawling</li>
 *   <li>Crawling execution monitoring and timing</li>
 * </ul>
 */
public class DataIndexHelper {

    /** Logger instance for this class */
    private static final Logger logger = LogManager.getLogger(DataIndexHelper.class);

    /** Parameter key for controlling deletion of old documents */

 * TreeTraverser<NodeType> traverser = TreeTraverser.using(node -> node.getChildNodes());
 * }
 *
 * @author Louis Wasserman
 * @since 15.0
 * @deprecated Use {@link com.google.common.graph.Traverser} instead. All instance methods have
 *     their equivalent on the result of {@code Traverser.forTree(tree)} where {@code tree}
 *     implements {@code SuccessorsFunction}, which has a similar API as {@link #children} or can be

 */
public class OpenSearchDataService extends AbstractCrawlerService implements DataService<OpenSearchAccessResult> {

    /**
     * Creates a new instance of OpenSearchDataService.
     * @param crawlerConfig The crawler configuration.
     */
    public OpenSearchDataService(final OpenSearchCrawlerConfig crawlerConfig) {
        index = crawlerConfig.getDataIndex();

      hp2 = hp.withDefaultPort(defaultPort);
      assertFalse(badDefaultPort);
    } catch (IllegalArgumentException e) {
      assertTrue(badDefaultPort);
    }

    // Check the pre-withDefaultPort() instance.
    if (expectHasExplicitPort) {
      assertTrue(hp.hasPort());
      assertEquals(expectPort, hp.getPort());
    } else {
      assertFalse(hp.hasPort());
      try {
        hp.getPort();

      hp2 = hp.withDefaultPort(defaultPort);
      assertFalse(badDefaultPort);
    } catch (IllegalArgumentException e) {
      assertTrue(badDefaultPort);
    }

    // Check the pre-withDefaultPort() instance.
    if (expectHasExplicitPort) {
      assertTrue(hp.hasPort());
      assertEquals(expectPort, hp.getPort());
    } else {
      assertFalse(hp.hasPort());
      try {
        hp.getPort();