import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import javax.annotation.CheckForNull;

/**
 * Base class for implementing services that can handle {@link #doStart} and {@link #doStop}
 * requests, responding to them with {@link #notifyStarted()} and {@link #notifyStopped()}
 * callbacks. Its subclasses must manage threads manually; consider {@link