code: @Override
    public OperableTrigger instantiate() {
  
      CronTriggerImpl ct = new CronTriggerImpl();
  
      try {
        ct.setCronExpression(cronExpression);
      } catch (ParseException e) {
        // all methods of construction ensure the expression is valid by this point...
        throw new RuntimeException(
            "CronExpression '"
                + cronExpression
                + "' is invalid, which should not be possible, please report bug to Quartz developers.");
      }
      ct.setTimeZone(tz);
      ct.setMisfireInstruction(misfireInstruction);
  
      return ct;
    }
docs: Build the actual Trigger -- NOT intended to be invoked by end users, but will rather be invoked
  by a TriggerBuilder which this ScheduleBuilder is given to.