* callbacks. Its subclasses must manage threads manually; consider {@link
 * AbstractExecutionThreadService} if you need only a single execution thread.
 *
 * @author Jesse Wilson
 * @author Luke Sandberg
 * @since 1.0
 */
@GwtIncompatible
@J2ktIncompatible
@ElementTypesAreNonnullByDefault
public abstract class AbstractService implements Service {