*/
    public void addExtension(CoreExtension coreExtension) {
        getExtensions().add(coreExtension);
    } // -- void addExtension( CoreExtension )

    /**
     * Method getExtensions.
     *
     * @return List
     */
    public List<CoreExtension> getExtensions() {
        if (this.extensions == null) {
            this.extensions = new ArrayList<CoreExtension>();
        }

                "http://maven.apache.org/EXTENSIONS/1.1.0 https://maven.apache.org/xsd/core-extensions-1.1.0.xsd");
        if ((coreExtensions.getExtensions() != null)
                && (coreExtensions.getExtensions().size() > 0)) {
            for (Iterator iter = coreExtensions.getExtensions().iterator(); iter.hasNext(); ) {
                CoreExtension o = (CoreExtension) iter.next();

        // TODO: destinationDirectory should be part of Javadoc
        javadocs.getRenderedDocumentation().from(javadocAll.flatMap(task -> (DirectoryProperty) task.getExtensions().getExtraProperties().get("destinationDirectory")));

        CheckstyleExtension checkstyle = project.getExtensions().getByType(CheckstyleExtension.class);
        tasks.register("checkstyleApi", Checkstyle.class, task -> {
            task.source(extension.getDocumentedSource());

    @Override
    public void apply(Project project) {
        ProjectLayout layout = project.getLayout();
        TaskContainer tasks = project.getTasks();

        GradleDocumentationExtension extension = project.getExtensions().getByType(GradleDocumentationExtension.class);
        generateDefaultImports(project, tasks, extension);
        generateUserManual(project, tasks, layout, extension);

                java.util.List<CoreExtension> extensions = coreExtensions.getExtensions();
                if (extensions == null) {
                    extensions = new java.util.ArrayList<CoreExtension>();
                }
                extensions.add(parseCoreExtension(parser, strict));
                coreExtensions.setExtensions(extensions);
            } else {
                checkUnknownElement(parser, strict);

                            List.copyOf(new CoreExtensionsStaxReader()
                                    .read(is, true, InputSource.of(extensionsFile.toString()))
                                    .getExtensions()),
                            allowMetaVersions);
                }
            }
            return List.of();
        } catch (XMLStreamException | IOException e) {

    }

    public List<Extension> getBuildExtensions() {
        Build build = getBuild();
        if ((build == null) || (build.getExtensions() == null)) {
            return Collections.emptyList();
        } else {
            return Collections.unmodifiableList(build.getExtensions());
        }
    }

    public void addProjectReference(MavenProject project) {
        projectReferences.put(

                            EMPTY,
                            problems,
                            errOn30,
                            Version.V20,
                            p.getExtensions(),
                            p.getKey(),
                            p);

                    validate20EffectivePluginDependencies(problems, p, request);
                }

            // extensionArtifacts
            Set<Artifact> extensionArtifacts = new HashSet<>();
            List<Extension> extensions =
                    project.getModel().getDelegate().getBuild().getExtensions();
            if (extensions != null) {
                for (Extension ext : extensions) {
                    String version;
                    if (ext.getVersion() == null || ext.getVersion().isEmpty()) {

    public boolean isExtensions() {
        return (getExtensions() != null) ? Boolean.parseBoolean(getExtensions()) : false;
    }
            ]]>
          </code>
        </codeSegment>
        <codeSegment>
          <version>4.0.0/4.0.99</version>
          <code>
            <![CDATA[
    public void setExtensions(boolean extensions) {
        setExtensions(String.valueOf(extensions));
    }

    /**