* supports it.
   */
  public static <T extends @Nullable Object> Iterator<T> concat(
      Iterator<? extends T> a, Iterator<? extends T> b) {
    checkNotNull(a);
    checkNotNull(b);
    return concat(consumingForArray(a, b));
  }

  /**
   * Combines three iterators into a single iterator. The returned iterator iterates across the

    assertEquals("d", itr2.next());
    assertEquals("c", itr2.next());
  }

  public void testConcatPartiallyAdvancedFirst() {
    Iterator<String> itr1 = Iterators.concat(singletonIterator("a"), Iterators.forArray("b", "c"));
    assertEquals("a", itr1.next());
    assertEquals("b", itr1.next());
    Iterator<String> itr2 = Iterators.concat(itr1, singletonIterator("d"));

   * iterator supports it.
   *
   * <p><b>Java 8+ users:</b> The {@code Stream} equivalent of this method is {@code
   * Stream.concat(a, b)}.
   */
  public static <T extends @Nullable Object> Iterable<T> concat(
      Iterable<? extends T> a, Iterable<? extends T> b) {
    return FluentIterable.concat(a, b);
  }

  /**
   * Combines three iterables into a single iterable. The returned iterable has an iterator that

    }

    @Inject
    public DefaultLifecycleRegistry(
            List<LifecycleProvider> providers, Map<String, org.apache.maven.lifecycle.Lifecycle> lifecycles) {
        super(
                concat(providers, new LifecycleWrapperProvider(lifecycles)),
                new CleanLifecycle(),
                new DefaultLifecycle(),
                new SiteLifecycle(),
                new WrapperLifecycle());

            implements ExtensibleEnumRegistry<T> {

        protected final Map<String, T> values;

        DefaultExtensibleEnumRegistry(List<P> providers, T... builtinValues) {
            values = Stream.<T>concat(
                            Stream.of(builtinValues), providers.stream().flatMap(p -> p.provides().stream()))
                    .collect(Collectors.toUnmodifiableMap(t -> t.id().toLowerCase(Locale.ROOT), t -> t));
        }

     * Do not include the POM artifact as the file can't be set anyway.
     */
    private Stream<org.apache.maven.artifact.Artifact> getProjectArtifacts(MavenProject project) {
        return Stream.concat(Stream.of(project.getArtifact()), project.getAttachedArtifacts().stream());
    }

    private String id(org.apache.maven.artifact.Artifact artifact) {
        return artifact.getGroupId()

        return new Result<>(hasErrors(problems), model, problems);
    }

    /**
     * New result consisting of given result and new problem. Convenience for newResult(result.get(),
     * concat(result.getProblems(),problems)).
     *
     * @param result
     * @param problem
     */
    public static <T> Result<T> addProblem(Result<T> result, ModelProblem problem) {

     * Retrieve a stream of the project's artifacts
     */
    private Stream<Artifact> getProjectArtifacts(MavenProject project) {
        Stream<org.apache.maven.artifact.Artifact> artifacts = Stream.concat(
                Stream.concat(
                        // pom artifact
                        Stream.of(new ProjectArtifact(project)),
                        // main project artifact if not a pom

                boolean recursive) {
            List<Callable<InterimResult>> tasks = pomFiles.stream()
                    .map(pomFile -> ((Callable<InterimResult>)
                            () -> build(projectIndex, pomFile, concat(aggregatorFiles, pomFile), root, recursive)))
                    .collect(Collectors.toList());
            try {
                List<Future<InterimResult>> futures = executor.invokeAll(tasks);

        this._testCache = Object.create(null)
    }

    _addPattern (pattern) {
        // #32
        if (pattern && pattern[KEY_IGNORE]) {
            this._rules = this._rules.concat(pattern._rules)
            this._added = true
            return
        }

        if (checkPattern(pattern)) {
            const rule = createRule(pattern, this._ignoreCase)
            this._added = true