public static <E> ImmutableSet<E> of() {
    return (ImmutableSet<E>) RegularImmutableSet.EMPTY;
  }

  /**
   * Returns an immutable set containing {@code element}. Preferred over {@link
   * Collections#singleton} for code consistency, {@code null} rejection, and because the return
   * type conveys the immutability guarantee.
   */
  public static <E> ImmutableSet<E> of(E element) {

public abstract class ImmutableSet<E> extends ImmutableCollection<E> implements Set<E> {
  ImmutableSet() {}

  public static <E> Collector<E, ?, ImmutableSet<E>> toImmutableSet() {
    return CollectCollectors.toImmutableSet();
  }

  // Casting to any type is safe because the set will never hold any elements.
  @SuppressWarnings({"unchecked"})
  public static <E> ImmutableSet<E> of() {

  public static <E> ImmutableSet<E> of() {
    return (ImmutableSet<E>) RegularImmutableSet.EMPTY;
  }

  /**
   * Returns an immutable set containing {@code element}. Preferred over {@link
   * Collections#singleton} for code consistency, {@code null} rejection, and because the return
   * type conveys the immutability guarantee.
   */
  public static <E> ImmutableSet<E> of(E element) {

    new EqualsTester()
        .addEqualityGroup(ImmutableSet.of(), ImmutableSet.of())
        .addEqualityGroup(ImmutableSet.of(1), ImmutableSet.of(1), ImmutableSet.of(1, 1))
        .addEqualityGroup(ImmutableSet.of(1, 2, 1), ImmutableSet.of(2, 1, 1))
        .testEquals();
  }

  /**
   * The maximum allowed probability of falsely detecting a hash flooding attack if the input is
   * randomly generated.
   */

  static final Iterable<Double> ALL_DOUBLE_CANDIDATES;
  static final Iterable<Double> DOUBLE_CANDIDATES_EXCEPT_NAN;

  static {
    ImmutableSet.Builder<Double> integralBuilder = ImmutableSet.builder();
    ImmutableSet.Builder<Double> fractionalBuilder = ImmutableSet.builder();
    integralBuilder.addAll(Doubles.asList(0.0, -0.0, Double.MAX_VALUE, -Double.MAX_VALUE));
    // Add small multiples of MIN_VALUE and MIN_NORMAL

        .addEqualityGroup(ImmutableSet.of(1), ImmutableSet.of(1), ImmutableSet.of(1, 1))
        .addEqualityGroup(ImmutableSet.of(1, 2, 1), ImmutableSet.of(2, 1, 1))
        .testEquals();
  }

  @GwtIncompatible("internals")
  public void testControlsArraySize() {
    ImmutableSet.Builder<String> builder = new ImmutableSet.Builder<String>();
    for (int i = 0; i < 10; i++) {
      builder.add("foo");

  private static final ImmutableSet<String> PS_NOT_RS =
      ImmutableSet.of("blogspot.com", "blogspot.co.uk", "uk.com");

  private static final ImmutableSet<String> PS =
      ImmutableSet.<String>builder().addAll(RS).addAll(PS_NOT_RS).build();

  private static final ImmutableSet<String> NO_PS =
      ImmutableSet.of("www", "foo.ihopethiswillneverbeapublicsuffix", "x.y.z");

  /**

    // invalidate setToTest
    wrappedSet.remove(1);
    // sanity check on update of wrappedSet
    assertThat(wrappedSet).isNotEqualTo(copyOfWrappedSet);

    ImmutableSet<Integer> copyOfModifiedSet = ImmutableSet.copyOf(wrappedSet); // {2,3}
    // sanity check on construction of copyOfModifiedSet
    assertThat(wrappedSet).isEqualTo(copyOfModifiedSet);

    // invalidate setToTest
    wrappedSet.remove(1);
    // sanity check on update of wrappedSet
    assertThat(wrappedSet).isNotEqualTo(copyOfWrappedSet);

    ImmutableSet<Integer> copyOfModifiedSet = ImmutableSet.copyOf(wrappedSet); // {2,3}
    // sanity check on construction of copyOfModifiedSet
    assertThat(wrappedSet).isEqualTo(copyOfModifiedSet);

    Set<Set<Integer>> expected = newHashSet();
    expected.add(ImmutableSet.<Integer>of());
    expected.add(ImmutableSet.of(1));
    expected.add(ImmutableSet.of(2));
    expected.add(ImmutableSet.of(3));
    expected.add(ImmutableSet.of(1, 2));
    expected.add(ImmutableSet.of(1, 3));
    expected.add(ImmutableSet.of(2, 3));
    expected.add(ImmutableSet.of(1, 2, 3));