// this is a live injected collection
    private final List<ClassRealmManagerDelegate> delegates;

    private final ClassRealm mavenApiRealm;

    /**
     * Patterns of artifacts provided by maven core and exported via maven api realm. These artifacts are filtered from
     * plugin and build extensions realms to avoid presence of duplicate and possibly conflicting classes on classpath.
     */
    private final Set<String> providedArtifacts;

                List<String> exports = exportedPackages.get(extensionRealm);

                if (exports == null || exports.isEmpty()) {
                    /*
                     * Most existing extensions don't define exported packages, i.e. no classes are to be exposed to
                     * plugins, yet the components provided by the extension (e.g. artifact handlers) must be

    <exportedPackage>org.fusesource.jansi.Ansi</exportedPackage>

    <!-- javax.inject (JSR-330) -->
    <exportedPackage>javax.inject.*</exportedPackage>
    <!-- javax.enterprise.inject (JSR-299): Must never be exported if needed at plugin level, plugin adds it
         there is no justification to get it at Maven level and leaking it will conflict.
    <exportedPackage>javax.enterprise.util.*</exportedPackage>

    /**
     * Gets the problems that were encountered during the settings building. Note that only problems of severity
     * {@link BuilderProblem.Severity#WARNING} and below are reported here. Problems with a higher severity level cause
     * the settings builder to fail with a {@link ToolchainsBuilderException}.
     *

    /**
     * OS family that can be tested for. {@value}
     */
    private static final String FAMILY_OS400 = "os/400";

    /**
     * OpenJDK is reported to call MacOS X "Darwin"
     *
     * @see <a href="https://issues.apache.org/bugzilla/show_bug.cgi?id=44889">bugzilla issue</a>
     * @see <a href="https://issues.apache.org/jira/browse/HADOOP-3318">HADOOP-3318</a>

                            + " is missing.",
                    dependency.getLocation(""));
            return null;
        }

        String imported = groupId + ':' + artifactId + ':' + version;

        if (importIds.contains(imported)) {
            StringBuilder message =
                    new StringBuilder("The dependencies of type=pom and with scope=import form a cycle: ");

            PluginDescriptor pluginDescriptor = null;
            if (plugin.isExtensions() && !artifacts.isEmpty()) {
                // ignore plugin descriptor parsing errors at this point
                // these errors will reported during calculation of project build execution plan
                try {
                    pluginDescriptor = extractPluginDescriptor(artifacts.get(0), plugin);

                        problems.add(
                                Severity.WARNING,
                                Version.V40,
                                "Ignored POM import for: " + toString(dependency) + " as already imported "
                                        + toString(present) + ".  Add a the conflicting managed dependency directly "
                                        + "to the dependencyManagement section of the POM.");

                .filter(rap -> !allAvailableProfiles.contains(rap))
                .collect(toSet());

        if (!notFoundRequiredProfiles.isEmpty()) {
            // Use SLF4J formatter for consistency with warnings reported by logger
            final String message = MessageFormatter.format(
                            "The requested profiles {} could not be activated or deactivated because they do not"

import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;

import org.apache.maven.api.model.Model;

/**
 * Holds all Models that are known to the reactor. This allows the project builder to resolve imported Models from the
 * reactor when building another project's effective model.
 *
 */
class ReactorModelPool {
    private final Map<GAKey, Set<Model>> modelsByGa = new ConcurrentHashMap<>();