code: @Nonnull
    public EChange unscheduleJob (@Nonnull final TriggerKey aTriggerKey)
    {
      ValueEnforcer.notNull (aTriggerKey, "TriggerKey");
      try
      {
        if (m_aScheduler.unscheduleJob (aTriggerKey))
        {
          LOGGER.info ("Succesfully unscheduled job with TriggerKey " + aTriggerKey.toString ());
          return EChange.CHANGED;
        }
      }
      catch (final SchedulerException ex)
      {
        LOGGER.error ("Failed to unschedule job with TriggerKey " + aTriggerKey.toString (), ex);
      }
      return EChange.UNCHANGED;
    }
docs: Unschedule the job with the specified trigger key as returned from
  {@link #scheduleJob(String, JDK8TriggerBuilder, Class, Map)}.
  
  @param aTriggerKey
  Trigger key to use. May not be <code>null</code>.
  @return {@link EChange}.