* won't cause a rehash.
   *
   * <p>As of jdk7u40, HashMap has an empty-map optimization. The argument to new HashMap(int) is
   * noted, but the initial table is a zero-length array.
   *
   * <p>This test may fail miserably on non-OpenJDK environments...
   */
  @J2ktIncompatible
  @GwtIncompatible // reflection