import java.util.Spliterator;
import java.util.function.Predicate;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * GWT emulated version of {@link ImmutableCollection}.
 *
 * @author Jesse Wilson
 */
@SuppressWarnings("serial") // we're overriding default serialization
@ElementTypesAreNonnullByDefault
public abstract class ImmutableCollection<E> extends AbstractCollection<E> implements Serializable {

 * {@link Collections#singleton(Object)} and <a
 * href="https://docs.oracle.com/javase/9/docs/api/java/util/Set.html#immutable">{@code Set.of}</a>,
 * we recommend using <i>these</i> classes instead for this reason (as well as for consistency).
 *
 * <h4>Creation</h4>
 *
 * <p>Except for logically "abstract" types like {@code ImmutableCollection} itself, each {@code

 * {@link Collections#singleton(Object)} and <a
 * href="https://docs.oracle.com/javase/9/docs/api/java/util/Set.html#immutable">{@code Set.of}</a>,
 * we recommend using <i>these</i> classes instead for this reason (as well as for consistency).
 *
 * <h4>Creation</h4>
 *
 * <p>Except for logically "abstract" types like {@code ImmutableCollection} itself, each {@code