code: public synchronized boolean resumeJobIfPresent(final String jobName, final String groupName)
        throws SchedulerException {
      if (ifJobExist(jobName, groupName)) {
        this.scheduler.resumeJob(new JobKey(jobName, groupName));
        return true;
      } else {
        return false;
      }
    }
docs: Resume a job.
  @param jobName
  @param groupName
  @return true the job has been resumed, no if the job doesn't exist.
  @throws SchedulerException