Class<X> exceptionType,
        AsyncFunction<? super X, ? extends V> fallback) {
      super(input, exceptionType, fallback);
    }

    @Override
    ListenableFuture<? extends V> doFallback(
        AsyncFunction<? super X, ? extends V> fallback, X cause) throws Exception {
      ListenableFuture<? extends V> replacement = fallback.apply(cause);
      checkNotNull(
          replacement,

        } else {
            boolean fallback = false;

            String[] tok = part1.split("\\.");
            int idx = 0;
            if (idx < tok.length) {
                majorVersion = getNextIntegerToken(tok[idx++]);
                if (majorVersion == null) {
                    fallback = true;
                }
            } else {
                fallback = true;
            }

   *
   * @param future The future attach the callback to.
   * @param callback The callback to invoke when {@code future} is completed.
   * @param executor The executor to run {@code callback} when the future completes.
   * @since 10.0
   */
  public static <V extends @Nullable Object> void addCallback(
      final ListenableFuture<V> future,
      final FutureCallback<? super V> callback,
      Executor executor) {

   *
   * @param future The future attach the callback to.
   * @param callback The callback to invoke when {@code future} is completed.
   * @param executor The executor to run {@code callback} when the future completes.
   * @since 10.0
   */
  public static <V extends @Nullable Object> void addCallback(
      final ListenableFuture<V> future,
      final FutureCallback<? super V> callback,
      Executor executor) {

        private final ArtifactRepositoryLayout fallback;

        UnknownRepositoryLayout(String id, ArtifactRepositoryLayout fallback) {
            this.id = id;
            this.fallback = fallback;
        }

        public String getId() {
            return id;
        }

        public String pathOf(Artifact artifact) {
            return fallback.pathOf(artifact);
        }

import java.io.PrintWriter;

import org.apache.maven.api.annotations.Nullable;
import org.apache.maven.api.cli.Logger;

/**
 * Proto {@link Logger}. Uses provided {@link PrintStream}s or {@link System} ones as fallback.
 * Supports only two levels: ERROR and WARNING, that is emitted to STDERR and STDOUT.
 */
public class ProtoLogger implements Logger {

    private final PrintWriter out;
    private final PrintWriter err;

                if (connectTimeoutXml != null) {
                    connectTimeout = Integer.parseInt(connectTimeoutXml.getValue());
                } else {
                    // fallback configuration name
                    PlexusConfiguration httpConfiguration = config.getChild("httpConfiguration", false);
                    if (httpConfiguration != null) {

        if (cacheResponse.code != HttpURLConnection.HTTP_GATEWAY_TIMEOUT) {
          return cacheResponse
        }
      } catch (ioe: IOException) {
        // Failures are ignored as we can fallback to the network
        // and hopefully repopulate the cache.
      }
    }

    return null
  }

  @Throws(Exception::class)
  private fun readResponse(
    hostname: String,

                    projectSelector.getOptionalProjectsBySelectors(request, allSortedProjects, optionalSelectors));

            // it can be empty when an optional project is missing from the reactor, fallback to returning all projects
            if (!selectedProjects.isEmpty()) {
                result = new ArrayList<>(selectedProjects);

                result = includeAlsoMakeTransitively(result, request, graph);

                    .println(messageBuilderFactory
                            .builder()
                            .warning(
                                    "Maven4 SecDispatcher disabled; Maven3 fallback may still work, use `mvnenc diag` to check")
                            .build());
            secDispatcher.writeConfiguration(config);
            return OK;
        }