code: @Nonnull
    public static CronScheduleBuilder cronSchedule (final String cronExpression)
    {
      try
      {
        return cronSchedule (new CronExpression (cronExpression));
      }
      catch (final ParseException e)
      {
        // all methods of construction ensure the expression is valid by
        // this point...
        throw new RuntimeException ("CronExpression '" + cronExpression + "' is invalid.", e);
      }
    }
docs: Create a CronScheduleBuilder with the given cron-expression string - which
  is presumed to b e valid cron expression (and hence only a RuntimeException
  will be thrown if it is not).
  
  @param cronExpression
  the cron expression string to base the schedule on.
  @return the new CronScheduleBuilder
  @throws RuntimeException
  wrapping a ParseException if the expression is invalid
  @see CronExpression