This method "CronExpression.isValidExpression()" will not work as expected.

[ssyyzs]

• If "L" is used alone on the seconds, minutes, hours, or months of an cron expression,
  but otherwise formatted correctly. This method CronExpression.isValidExpression will return true, but the actual expression is wrong and should return false. For example:

CronExpression.isValidExpression("L 30 * * * ?"); // will return true

• However, when we calculate the next trigger time through TriggerUtils.computeFireTimes() with this expression, an NoSuchElementException will be thrown. For Example :

TriggerUtils.computeFireTimes(new CronExpression("L 30 * * * ?"), null, 5); // throw runtime exception

• Is it better to return a ParseException when constructing a CronExpression in this case?