code: @SuppressWarnings("unused")
      public void setCronExpression(String cronExpression) {
  
          checkFrozen();
  
          try {
              // check if the cron expression is valid
              new CronExpression(cronExpression);
          } catch (Exception e) {
              throw new CmsIllegalArgumentException(
                  Messages.get().container(Messages.ERR_BAD_CRON_EXPRESSION_2, getJobName(), cronExpression));
          }
  
          m_cronExpression = cronExpression;
      }
docs: Sets the cron expression for this job entry.<p>
  
  @param cronExpression the cron expression to set