throws InterruptedException {
    while (!isThreadBlockedOnInstanceOf(t, blocker)) {
      if (t.getState() == Thread.State.TERMINATED) {
        throw new RuntimeException("Thread " + t + " exited unexpectedly");
      }
      Thread.sleep(1);
    }
  }

  private static boolean isThreadBlockedOnInstanceOf(Thread t, Class<?> blocker) {

      throws InterruptedException {
    while (!isThreadBlockedOnInstanceOf(t, blocker)) {
      if (t.getState() == Thread.State.TERMINATED) {
        throw new RuntimeException("Thread " + t + " exited unexpectedly");
      }
      Thread.sleep(1);
    }
  }

  private static boolean isThreadBlockedOnInstanceOf(Thread t, Class<?> blocker) {

                logger.info("ThumbnailGenerator is stopped.");
            }
            exitCode = Constants.EXIT_FAIL;
        } catch (final Throwable t) {
            logger.error("ThumbnailGenerator terminated unexpectedly.", t);
            exitCode = Constants.EXIT_FAIL;
        } finally {
            if (systemMonitorTask != null) {
                systemMonitorTask.cancel();
            }

                logger.info("SuggestCreator is stopped.");
            }
            exitCode = Constants.EXIT_FAIL;
        } catch (final Throwable t) {
            logger.error("SuggestCreator terminated unexpectedly.", t);
            exitCode = Constants.EXIT_FAIL;
        } finally {
            if (systemMonitorTask != null) {
                systemMonitorTask.cancel();
            }

     *
     * - _can_ be null without causing a runtime failure (because we don't want the interesting
     *   details of precondition failure to be hidden by an exception we throw about an unexpectedly
     *   null _failure message_)
     *
     * That combination upsets NullPointerTester, which wants any call that passes null for a
     * non-@Nullable parameter to trigger a NullPointerException.
     *

     *
     * - _can_ be null without causing a runtime failure (because we don't want the interesting
     *   details of precondition failure to be hidden by an exception we throw about an unexpectedly
     *   null _failure message_)
     *
     * That combination upsets NullPointerTester, which wants any call that passes null for a
     * non-@Nullable parameter to trigger a NullPointerException.
     *

                logger.info("Crawler is stopped.");
            }
            exitCode = Constants.EXIT_FAIL;
        } catch (final Throwable t) {
            logger.error("Crawler terminated unexpectedly.", t);
            exitCode = Constants.EXIT_FAIL;
        } finally {
            if (commandThread != null && commandThread.isAlive()) {
                commandThread.interrupt();
            }