It is important to know some key objects of Quartz.

org.quartz.Trigger 

The base abstract class to be extended by all Triggers including org.quartz.CronTrigger.

Triggers s have a name and group associated with them, which should uniquely identify them within a single Scheduler.

Triggers are the ‘mechanism’ by which Jobs are scheduled. Many Triggers can point to the same Job, but a single Trigger can only point to one Job.

We can use getNextFireTime() to get the next time at which the trigger will fire and getPreviousFireTime() to get the time at which the trigger should occur.

org.quartz.JobDetail   

Conveys the detail properties of a given Job instance.

Quartz does not store an actual instance of a Job class, but instead allows you to define an instance of one, through the use of a JobDetail.

Job have a name and group associated with them, which should uniquely identify them within a single

Scheduler.