final ModelProcessor modelLocator;

    final Map<String, String> userProperties = new ConcurrentHashMap<>();

    final Map<Path, Holder> modelByPath = new ConcurrentHashMap<>();

    final Map<GAKey, Holder> modelByGA = new ConcurrentHashMap<>();

    public static class Holder {
        private volatile boolean set;
        private volatile Model model;

        Holder() {}

    }

    /**
     * {@link ConcurrentHashMap}の新しいインスタンスを作成して返します。
     *
     * @param <K>
     *            {@link ConcurrentHashMap}のキーの型
     * @param <V>
     *            {@link ConcurrentHashMap}の値の型
     * @return {@link ConcurrentHashMap}の新しいインスタンス
     * @see ConcurrentHashMap#ConcurrentHashMap()
     */
    public static <K, V> ConcurrentHashMap<K, V> newConcurrentHashMap() {

        val rootProjectDir: DirectoryProperty
    }

    @get:Inject
    abstract val execOperations: ExecOperations

    private
    val suspiciousDaemons = ConcurrentHashMap<String, MutableSet<String>>()

    private
    val daemonPids = ConcurrentHashMap.newKeySet<String>()

    private
    val logger = Logging.getLogger(DaemonTracker::class.java)

    override fun close() {

        ConcurrentHashMap<Object, Supplier<?>> cache;
        RepositoryCache repositoryCache = session.getCache();
        if (repositoryCache == null) {
            cache = new ConcurrentHashMap<>();
        } else {
            cache = (ConcurrentHashMap<Object, Supplier<?>>)
                    repositoryCache.computeIfAbsent(session, KEY, ConcurrentHashMap::new);
        }

    private final TypeRegistry typeRegistry;

    private final ConcurrentHashMap<String, ArtifactHandler> allHandlers;

    @Inject
    public DefaultArtifactHandlerManager(TypeRegistry typeRegistry) {
        this.typeRegistry = requireNonNull(typeRegistry, "null typeRegistry");
        this.allHandlers = new ConcurrentHashMap<>();
    }

    @Override
    public void onEvent(Object event) {

  private static final String TEST_KEY = "test key";
  private static final String TEST_VALUE = "test value";

  // Non-loading versions:
  private final Map<Object, Object> map = new MapMaker().makeMap(); // Returns ConcurrentHashMap
  private final Cache<Object, Object> cache = CacheBuilder.newBuilder().recordStats().build();
  private final Cache<Object, Object> cacheNoStats = CacheBuilder.newBuilder().build();

  @BeforeExperiment
  void setUp() {

    // GWT's ConcurrentHashMap is a wrapper around HashMap, but it rejects null keys, which matches
    // the behaviour of the non-GWT implementation of newConcurrentHashSet().
    // On the other hand HashSet might be better for code size if apps aren't
    // already using Collections.newSetFromMap and ConcurrentHashMap.
    return Collections.newSetFromMap(new ConcurrentHashMap<E, Boolean>());
  }

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<>();

import javax.inject.Inject;
import javax.inject.Named;
import javax.inject.Singleton;

import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.concurrent.ConcurrentHashMap;
import java.util.stream.Collectors;

import org.apache.maven.api.JavaPathType;
import org.apache.maven.api.Type;
import org.apache.maven.api.annotations.Nonnull;

 * existing multiset values.
 *
 * @author mike nonemacher
 */

public class ConcurrentHashMultisetBasherTest extends TestCase {

  public void testAddAndRemove_ConcurrentHashMap() throws Exception {
    testAddAndRemove(new ConcurrentHashMap<String, AtomicInteger>());
  }

  public void testAddAndRemove_ConcurrentSkipListMap() throws Exception {
    testAddAndRemove(new ConcurrentSkipListMap<String, AtomicInteger>());
  }