* scattered in memory and thus don't interfere much with each
   * other. But Atomic objects residing in arrays will tend to be
   * placed adjacent to each other, and so will most often share
   * cache lines (with a huge negative performance impact) without
   * this precaution.
   *
   * In part because Cells are relatively large, we avoid creating

 * object.
 *
 * <p><b>Comparison to {@code java.util.Optional} (JDK 8 and higher):</b> A new {@code Optional}
 * class was added for Java 8. The two classes are extremely similar, but incompatible (they cannot
 * share a common supertype). <i>All</i> known differences are listed either here or with the
 * relevant methods below.
 *
 * <ul>
 *   <li>This class is serializable; {@code java.util.Optional} is not.

      return samples;
    }

    @Override
    public Set<V> create(Object... elements) {
      @SuppressWarnings("unchecked")
      V[] valuesArray = (V[]) elements;

      // Start with a suitably shaped collection of entries
      Collection<Entry<K, V>> originalEntries = mapGenerator.getSampleElements(elements.length);

      // Create a copy of that, with the desired value for each value

import java.util.concurrent.ConcurrentSkipListMap;

/**
 * A microbenchmark that tests the performance of get() and iteration on various map
 * implementations. Forked from {@link SetContainsBenchmark}.
 *
 * @author Nicholaus Shupe
 */
public class MapBenchmark {
  @Param({"Hash", "LinkedHM", "MapMaker1", "Immutable"})
  private Impl impl;

  public enum Impl {
    Hash {
      @Override

 *
 * <pre>{@code
 * public class MyServer implements Closeable {
 *   private static final FinalizableReferenceQueue frq = new FinalizableReferenceQueue();
 *   // You might also share this between several objects.
 *
 *   private static final Set<Reference<?>> references = Sets.newConcurrentHashSet();
 *   // This ensures that the FinalizablePhantomReference itself is not garbage-collected.
 *

 *
 * <pre>{@code
 * public class MyServer implements Closeable {
 *   private static final FinalizableReferenceQueue frq = new FinalizableReferenceQueue();
 *   // You might also share this between several objects.
 *
 *   private static final Set<Reference<?>> references = Sets.newConcurrentHashSet();
 *   // This ensures that the FinalizablePhantomReference itself is not garbage-collected.
 *