* | `http://host/?a=apple&b`          | `["a", "b"]`            |
   */
  @get:JvmName("queryParameterNames")
  val queryParameterNames: Set<String>
    get() {
      if (queryNamesAndValues == null) return emptySet()
      val result = LinkedHashSet<String>(queryNamesAndValues.size / 2, 1.0F)
      for (i in 0 until queryNamesAndValues.size step 2) {
        result.add(queryNamesAndValues[i]!!)
      }

  }

  /**
   * Creates an empty {@code CopyOnWriteArraySet} instance.
   *
   * <p><b>Note:</b> if you need an immutable empty {@link Set}, use {@link Collections#emptySet}
   * instead.
   *
   * @return a new, empty {@code CopyOnWriteArraySet}
   * @since 12.0
   */
  @J2ktIncompatible
  @GwtIncompatible // CopyOnWriteArraySet