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 {
  static final int SPLITERATOR_CHARACTERISTICS =

        Collection<?> collection = (Collection<?>) elements;
        getReadyToExpandTo(size + collection.size());
        if (collection instanceof ImmutableCollection) {
          ImmutableCollection<?> immutableCollection = (ImmutableCollection<?>) collection;
          size = immutableCollection.copyIntoArray(contents, size);
          return this;
        }
      }
      super.addAll(elements);
      return this;
    }
  }

    }

    /**
     * Returns a newly-created {@code ImmutableCollection} of the appropriate type, containing the
     * elements provided to this builder.
     *
     * <p>Note that each builder class covariantly returns the appropriate type of {@code
     * ImmutableCollection} from this method.
     */
    public abstract ImmutableCollection<E> build();
  }