import java.util.Collections;
import java.util.Set;

/**
 * GWT emulation of {@link RegularImmutableSet}.
 *
 * @author Hayward Chan
 */
final class RegularImmutableSet<E> extends ForwardingImmutableSet<E> {
  static final RegularImmutableSet<Object> EMPTY =
      new RegularImmutableSet<Object>(Collections.emptySet());

  RegularImmutableSet(Set<E> delegate) {
    super(delegate);
  }

  }

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

  public static <E> ImmutableSet<E> of(E e1) {
    return new SingletonImmutableSet<E>(e1);
  }

  @SuppressWarnings("unchecked")
  public static <E> ImmutableSet<E> of(E e1, E e2) {