/**
     * Creates and returns a new instance of {@link ConcurrentHashMap}.
     *
     * @param <K> the key type of {@link ConcurrentHashMap}
     * @param <V> the value type of {@link ConcurrentHashMap}
     * @return a new instance of {@link ConcurrentHashMap}
     * @see ConcurrentHashMap#ConcurrentHashMap()
     */
    public static <K, V> ConcurrentHashMap<K, V> newConcurrentHashMap() {
        return new ConcurrentHashMap<>();

   * @since 15.0
   */
  public static <E> Set<E> newConcurrentHashSet() {
    return Collections.newSetFromMap(new ConcurrentHashMap<E, Boolean>());
  }

  /**
   * Creates a thread-safe set backed by a hash map and containing the given elements. The set is
   * backed by a {@link ConcurrentHashMap} instance, and thus carries the same concurrency
   * guarantees.
   *

import java.util.Enumeration;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.regex.Pattern;
import java.util.stream.Collectors;
import java.util.stream.Stream;

import javax.naming.directory.Attribute;
import javax.naming.directory.BasicAttribute;

/**
 * The concurrent hash map implementation built by {@link MapMaker}.
 *
 * <p>This implementation is heavily derived from revision 1.96 of <a
 * href="http://tinyurl.com/ConcurrentHashMap">ConcurrentHashMap.java</a>.
 *
 * @param <K> the type of the keys in the map
 * @param <V> the type of the values in the map
 * @param <E> the type of the {@link InternalEntry} entry implementation used internally

import java.util.Date;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.regex.Matcher;