* ({@link PluginDescriptor#getPluginLookupKey()}). Plugin contexts itself are mappings of {@link String} keys to
     * {@link Object} values.
     */
    private final ConcurrentMap<String, ConcurrentMap<String, ConcurrentMap<String, Object>>>
            pluginContextsByProjectAndPluginKey = new ConcurrentHashMap<>();

    public void setProjects(List<MavenProject> projects) {
        if (!projects.isEmpty()) {

  // currently only package visible.
  abstract class AbstractCacheSet<T> extends AbstractSet<T> {
    final ConcurrentMap<?, ?> map;

    AbstractCacheSet(ConcurrentMap<?, ?> map) {
      this.map = map;
    }

    @Override
    public int size() {
      return map.size();
    }

    @Override
    public boolean isEmpty() {

import java.util.SortedSet;
import java.util.UUID;
import java.util.concurrent.BlockingDeque;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.ConcurrentNavigableMap;
import java.util.concurrent.ConcurrentSkipListMap;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.Executor;

import com.google.common.collect.ImmutableSet;
import com.google.common.testing.NullPointerTester;
import java.lang.Thread.UncaughtExceptionHandler;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.atomic.AtomicReference;
import junit.framework.TestCase;
import org.jspecify.annotations.NullUnmarked;

/**
 * @author Charles Fry
 */

        ConcurrentMap<K, V> newMap = new MapMaker().weakValues().makeMap();
        checkState(newMap instanceof MapMakerInternalMap);
        newMap.putAll(map);
        return newMap;
      }
    },
    MapMakerWeakKeysStrongValues {
      @Override
      public <K extends Comparable<K>, V> Map<K, V> create(Map<K, V> map) {
        ConcurrentMap<K, V> newMap = new MapMaker().weakKeys().makeMap();

                }
            }
        }
        return null;
    }

    @SuppressWarnings("unchecked")
    private ConcurrentMap<Key, PluginVersionResult> getCache(PluginVersionRequest request) {
        SessionData data = request.getRepositorySession().getData();
        return (ConcurrentMap<Key, PluginVersionResult>)
                data.computeIfAbsent(CACHE_KEY, () -> new ConcurrentHashMap<>(256));
    }

        private final int maxCountLimit;
        private final AtomicInteger totalCount;
        private final ConcurrentMap<BuilderProblem.Severity, LongAdder> counters;
        private final ConcurrentMap<BuilderProblem.Severity, List<P>> problems;
        private final Predicate<? super P> filter;

      }
    };
  }

  private static final String KEY = "puppies";

  ConcurrentMap<String, AtomicInteger> backingMap;
  ConcurrentHashMultiset<String> multiset;

  @SuppressWarnings("unchecked")
  @Override
  protected void setUp() {
    backingMap = mock(ConcurrentMap.class);
    when(backingMap.isEmpty()).thenReturn(true);

    multiset = ConcurrentHashMultiset.create(backingMap);

   * @since 20.0
   */
  public static <E> ConcurrentHashMultiset<E> create(ConcurrentMap<E, AtomicInteger> countMap) {
    checkArgument(countMap.isEmpty(), "the backing map (%s) must be empty", countMap);
    return new ConcurrentHashMultiset<>(countMap);
  }

  private ConcurrentHashMultiset(ConcurrentMap<E, AtomicInteger> countMap) {
    this.countMap = countMap;
  }

  // Query Operations

    assertFreshInstance(new TypeToken<NavigableMap<?, ?>>() {});
  }

  public void testConcurrentMap() {
    assertFreshInstance(new TypeToken<ConcurrentMap<String, ?>>() {});
    assertCanGenerateOnly(
        new TypeToken<ConcurrentMap<EmptyEnum, String>>() {}, Maps.newConcurrentMap());
  }

  public void testMultimap() {
    assertFreshInstance(new TypeToken<Multimap<String, ?>>() {});
  }