* or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.util.concurrent;

import static com.google.common.collect.Sets.newConcurrentHashSet;
import static java.util.Objects.requireNonNull;
import static java.util.concurrent.atomic.AtomicIntegerFieldUpdater.newUpdater;
import static java.util.concurrent.atomic.AtomicReferenceFieldUpdater.newUpdater;

    return Sets.newHashSetWithExpectedSize(expectedSize);
  }

  static <E extends @Nullable Object> Set<E> newConcurrentHashSet() {
    // 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

    return Sets.newHashSetWithExpectedSize(expectedSize);
  }

  /** Returns the platform preferred implementation of a thread-safe hash set. */
  static <E> Set<E> newConcurrentHashSet() {
    return ConcurrentHashMap.newKeySet();
  }

  /**
   * Returns the platform preferred implementation of an insertion ordered set based on a hash
   * table.
   */

  static class MyServerExampleWithFrq implements Closeable {
    private static final FinalizableReferenceQueue frq = new FinalizableReferenceQueue();

    private static final Set<Reference<?>> references = Sets.newConcurrentHashSet();

    private final ServerSocket serverSocket;

    private MyServerExampleWithFrq() throws IOException {
      this.serverSocket = new ServerSocket(0);
    }

  static class MyServerExampleWithFrq implements Closeable {
    private static final FinalizableReferenceQueue frq = new FinalizableReferenceQueue();

    private static final Set<Reference<?>> references = Sets.newConcurrentHashSet();

    private final ServerSocket serverSocket;

    private MyServerExampleWithFrq() throws IOException {
      this.serverSocket = new ServerSocket(0);
    }