* putIndex or sees null item.
     */
    private void checkNext() {
      if (nextIndex == putIndex) {
        nextIndex = -1;
        nextItem = null;
      } else {
        nextItem = items[nextIndex];
        if (nextItem == null) nextIndex = -1;
      }
    }

    @Override
    public E next() {

            Element build = root.child("build").orElse(null);
            Element plugins = build.child("plugins").orElse(null);
            Element cleanPlugin = plugins.child("plugin").orElse(null);
            Element executions = cleanPlugin.child("executions").orElse(null);
            Element execution = executions.child("execution").orElse(null);
            Element phase = execution.child("phase").orElse(null);

        if (settings.isUsePluginRegistry()) {
            addViolation(problems, Severity.WARNING, "usePluginRegistry", null, "is deprecated and has no effect.");
        }

        List<String> pluginGroups = settings.getPluginGroups();

        if (pluginGroups != null) {
            for (int i = 0; i < pluginGroups.size(); i++) {
                String pluginGroup = pluginGroups.get(i).trim();

    node.thread = null; // mark as 'deleted'
    restart:
    while (true) {
      Waiter pred = null;
      Waiter curr = waitersField;
      if (curr == Waiter.TOMBSTONE) {
        return; // give up if someone is calling complete
      }
      Waiter succ;
      while (curr != null) {
        succ = curr.next;
        if (curr.thread != null) { // we aren't unlinking this node, update pred.

                artifacts, projectArtifact.artifact, null, null, null, source, filter, Collections.emptyList(), null);
    }

    private ArtifactResolutionResult collect(ArtifactSpec a) throws ArtifactResolutionException {
        return artifactCollector.collect(
                Collections.singleton(a.artifact),
                projectArtifact.artifact,
                null,
                null,
                null,

     */
    @Nonnull
    ProjectBuilderResult build(ProjectBuilderRequest request) throws ProjectBuilderException;

    /**
     * Creates a {@link org.apache.maven.api.Project} from a POM file.
     *
     * @param session the {@link Session}, must not be {@code null}
     * @param source The {@link Source}, must not be {@code null}

        int exitCode = new MavenUpCling().run(args, null, null, null, false);
        System.exit(exitCode);
    }

    /**
     * ClassWorld Launcher "enhanced" entry point: returning exitCode and accepts Class World.
     */
    public static int main(String[] args, ClassWorld world) throws IOException {
        return new MavenUpCling(world).run(args, null, null, null, false);
    }

    /**

    protected final List<MojoExecution> executions = Collections.synchronizedList(new ArrayList<>());

    public MojoExecutorStub() {
        super(null, null, null, null, null, null);
    }

    public MojoExecutorStub(
            BuildPluginManager pluginManager,
            MavenPluginManager mavenPluginManager,
            LifecycleDependencyResolver lifeCycleDependencyResolver,

    protected void assertObjectNotNull(String variableName, Object value) {
        if (variableName == null) {
            String msg = "The value should not be null: variableName=null value=" + value;
            throw new IllegalArgumentException(msg);
        }
        if (value == null) {
            String msg = "The value should not be null: variableName=" + variableName;
            throw new IllegalArgumentException(msg);
        }

        doUpdate(entity, null);
    }

    public void insertOrUpdate(FileConfig entity) {
        doInsertOrUpdate(entity, null, null);
    }

    public void insertOrUpdate(FileConfig entity, RequestOptionCall<IndexRequestBuilder> opLambda) {
        entity.asDocMeta().indexOption(opLambda);
        doInsertOrUpdate(entity, null, null);
    }

    public void delete(FileConfig entity) {