private volatile boolean set;
        private volatile Model model;

        Holder() {}

        Holder(Model model) {
            this.model = Objects.requireNonNull(model);
            this.set = true;
        }

        public static Model deref(Holder holder) {
            return holder != null ? holder.get() : null;
        }

        public Model get() {
            if (!set) {

import java.util.Collections;
import java.util.LinkedHashSet;
import java.util.Set;

import org.apache.maven.lifecycle.LifeCyclePluginAnalyzer;
import org.apache.maven.model.Plugin;
import org.apache.maven.model.PluginExecution;

/**
 */
public class LifeCyclePluginAnalyzerStub implements LifeCyclePluginAnalyzer {
    public Set<Plugin> getPluginsBoundByDefaultToAllLifecycles(String packaging) {

            @Override
            public Model getRawModel(Path from, String gId, String aId) {
                Model model = findRawModel(from, gId, aId);
                if (model != null) {
                    context.modelByGA.put(new GAKey(gId, aId), new Holder(model));
                    context.modelByPath.put(model.getPomFile(), new Holder(model));
                }
                return model;
            }

            @Override

 */
package org.apache.maven.internal.impl.model;

import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamReader;

import java.io.IOException;
import java.io.InputStream;
import java.nio.file.Files;
import java.nio.file.Path;

import com.ctc.wstx.stax.WstxInputFactory;
import org.apache.maven.api.di.Named;
import org.apache.maven.api.services.model.*;

@Named

import org.apache.maven.api.services.ModelProblem;

/**
 * Collects the output of the model builder.
 *
 */
class DefaultModelBuilderResult implements ModelBuilderResult {
    private Model fileModel;
    private Model activatedFileModel;

    private Model effectiveModel;

    private List<String> modelIds;

    private Map<String, Model> rawModels;

    private Map<String, List<Profile>> activePomProfiles;

            Model model = new Model();
            model.setModelVersion("4.0.0");
            model.setGroupId(groupId);
            model.setArtifactId(artifactId);
            model.setVersion(version);
            model.setBuild(new Build());
            project = new MavenProject(model);
        }

        public ProjectBuilder setGroupId(String groupId) {

 *
 */
public class ModelResolverException extends MavenException {

    /**
     * The group id of the unresolvable model.
     */
    private final String groupId;

    /**
     * The artifact id of the unresolvable model.
     */
    private final String artifactId;

    /**
     * The version of the unresolvable model.
     */
    private final String version;

import org.apache.maven.model.building.ArtifactModelSource;
import org.apache.maven.model.building.DefaultModelProblem;
import org.apache.maven.model.building.FileModelSource;
import org.apache.maven.model.building.ModelSource2;
import org.apache.maven.model.building.ModelSource3;
import org.apache.maven.model.resolution.UnresolvableModelException;
import org.apache.maven.model.root.RootLocator;

     *
     * @param model The model into which to merge the values specified by its plugin management section, must not be
     *            <code>null</code>.
     * @param request The model building request that holds further settings, must not be {@code null}.
     * @param problems The container used to collect problems that were encountered, must not be {@code null}.
     */

 * under the License.
 */
package org.apache.maven.api.services.model;

import org.apache.maven.api.Version;
import org.apache.maven.api.VersionConstraint;
import org.apache.maven.api.VersionRange;
import org.apache.maven.api.annotations.Nonnull;
import org.apache.maven.api.services.VersionParserException;

/**
 * Model builder specific version parser. It is intentionally not