* See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import static com.google.common.collect.ImmutableSet.toImmutableSet;
import static com.google.common.truth.Truth.assertThat;
import static java.util.Collections.singleton;
import static org.junit.Assert.assertThrows;

import com.google.common.annotations.GwtCompatible;

    return (Collector) TO_IMMUTABLE_LIST;
  }

  // Sets

  @SuppressWarnings({"rawtypes", "unchecked"})
  static <E> Collector<E, ?, ImmutableSet<E>> toImmutableSet() {
    return (Collector) TO_IMMUTABLE_SET;
  }

  static <E> Collector<E, ?, ImmutableSortedSet<E>> toImmutableSortedSet(
      Comparator<? super E> comparator) {
    checkNotNull(comparator);

    return (Collector) TO_IMMUTABLE_LIST;
  }

  // Sets

  @SuppressWarnings({"rawtypes", "unchecked"})
  static <E> Collector<E, ?, ImmutableSet<E>> toImmutableSet() {
    return (Collector) TO_IMMUTABLE_SET;
  }

  static <E> Collector<E, ?, ImmutableSortedSet<E>> toImmutableSortedSet(
      Comparator<? super E> comparator) {
    checkNotNull(comparator);

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() {

    return new SerializedForm<E>(comparator, toArray());
  }

  /**
   * Not supported. Use {@link #toImmutableSortedSet} instead. This method exists only to hide
   * {@link ImmutableSet#toImmutableSet} from consumers of {@code ImmutableSortedSet}.
   *
   * @throws UnsupportedOperationException always
   * @deprecated Use {@link ImmutableSortedSet#toImmutableSortedSet}.

   * duplicates removed.
   *
   * <p><b>{@code Stream} equivalent:</b> pass {@link ImmutableSet#toImmutableSet} to {@code
   * stream.collect()}.
   *
   * @throws NullPointerException if any element is {@code null}
   * @since 14.0 (since 12.0 as {@code toImmutableSet()}).
   */
  @SuppressWarnings("nullness") // Unsafe, but we can't do much about it now.

   * duplicates removed.
   *
   * <p><b>{@code Stream} equivalent:</b> pass {@link ImmutableSet#toImmutableSet} to {@code
   * stream.collect()}.
   *
   * @throws NullPointerException if any element is {@code null}
   * @since 14.0 (since 12.0 as {@code toImmutableSet()}).
   */
  @SuppressWarnings("nullness") // Unsafe, but we can't do much about it now.

   * @since 33.2.0 (available since 21.0 in guava-jre)
   */
  @IgnoreJRERequirement // Users will use this only if they're already using streams.
  public static <E> Collector<E, ?, ImmutableSet<E>> toImmutableSet() {
    return CollectCollectors.toImmutableSet();
  }

  /**
   * Returns the empty immutable set. Preferred over {@link Collections#emptySet} for code
   * consistency, and because the return type conveys the immutability guarantee.
   *

   * {@link ImmutableSet#toImmutableSet} from consumers of {@code ImmutableSortedSet}.
   *
   * @throws UnsupportedOperationException always
   * @deprecated Use {@link ImmutableSortedSet#toImmutableSortedSet}.
   * @since 21.0
   */
  @DoNotCall("Use toImmutableSortedSet")
  @Deprecated
  public static <E> Collector<E, ?, ImmutableSet<E>> toImmutableSet() {
    throw new UnsupportedOperationException();

   * duplicate in encounter order will appear in the result.
   *
   * @since 21.0
   */
  public static <E> Collector<E, ?, ImmutableSet<E>> toImmutableSet() {
    return CollectCollectors.toImmutableSet();
  }

  /**
   * Returns the empty immutable set. Preferred over {@link Collections#emptySet} for code
   * consistency, and because the return type conveys the immutability guarantee.
   *