// 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>());
  }

        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) {

import jakarta.annotation.PreDestroy;

public class ProcessHelper {
    private static final Logger logger = LogManager.getLogger(ProcessHelper.class);

    protected final ConcurrentHashMap<String, JobProcess> runningProcessMap = new ConcurrentHashMap<>();

    protected int processDestroyTimeout = 10;

    @PreDestroy
    public void destroy() {
        for (final String sessionId : runningProcessMap.keySet()) {

   * figure out what to do with <a
   * href="https://github.com/openjdk/jdk/blob/c25c4896ad9ef031e3cddec493aef66ff87c48a7/src/java.base/share/classes/java/util/concurrent/ConcurrentHashMap.java#L4830">{@code
   * ConcurrentHashMap} support for {@code entrySet().add()}</a>.
   */
  @J2ktIncompatible
  @GwtIncompatible // reflection
  public static Method getAddAllUnsupportedNonePresentMethod() {

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;

class DefaultTransformerContext implements TransformerContext {
    final ModelLocator 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() {}

import com.google.common.annotations.J2ktIncompatible;
import com.google.common.base.Function;
import com.google.common.testing.NullPointerTester;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CountDownLatch;
import junit.framework.TestCase;

/**
 * @author Charles Fry
 */
@GwtCompatible(emulated = true)
@J2ktIncompatible // MapMaker

 * under the License.
 */
package org.apache.maven.cli.transfer;

import java.io.File;
import java.io.PrintWriter;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

import org.apache.maven.jline.JLineMessageBuilderFactory;

import com.google.common.annotations.J2ktIncompatible;
import com.google.common.base.Function;
import com.google.common.testing.NullPointerTester;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CountDownLatch;
import junit.framework.TestCase;

/**
 * @author Charles Fry
 */
@GwtCompatible(emulated = true)
@J2ktIncompatible // MapMaker