Quartz 2.2.x Demo - It shows cron job which executes twice every minute

gistfile1.java

import java.text.ParseException;
import java.util.Date;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

import org.quartz.CronScheduleBuilder;
import org.quartz.CronTrigger;
import org.quartz.Job;
import org.quartz.JobBuilder;
import org.quartz.JobDetail;
import org.quartz.JobExecutionContext;
import org.quartz.JobExecutionException;
import org.quartz.JobKey;
import org.quartz.Scheduler;
import org.quartz.SchedulerException;
import org.quartz.SchedulerFactory;
import org.quartz.Trigger;
import org.quartz.TriggerBuilder;
import org.quartz.impl.StdSchedulerFactory;

public class QuartzCronDemo {

	public static void main(String[] args) throws ParseException, SchedulerException {
		new QuartzCronDemo().schedule(args);
	}

	public void schedule(String[] args) throws ParseException, SchedulerException {
		SchedulerFactory factory = new StdSchedulerFactory();
		Scheduler scheduler = factory.getScheduler();
		Map<JobDetail, Set<? extends Trigger>> triggersAndJobs = new HashMap<JobDetail, Set<? extends Trigger>>();
		Set<CronTrigger> triggerList = new HashSet<CronTrigger>();
		String groupName = "GroupName";
		String jobName = "JobName";
		JobKey jobKey = new JobKey(jobName, groupName);
		String triggerName = jobName;
		JobDetail job = JobBuilder.newJob(MyCronJob.class).withIdentity(jobKey).usingJobData("groupName", groupName)
				.usingJobData("jobName", jobName).build();
	  // Cron expression for executing job twice in a minute.
		String[] cronExpressions = new String[] {
			"0 * * ? * SUN-SAT",
			"30 * * ? * SUN-SAT"
		};
		for (int i = 0; i < cronExpressions.length; i++) {
			CronTrigger trigger = (CronTrigger) TriggerBuilder.newTrigger().withIdentity(triggerName + i, groupName)
					.withSchedule(CronScheduleBuilder.cronSchedule(cronExpressions[i])).build();
			triggerList.add(trigger);
		}
		triggersAndJobs.put(job, triggerList);
		scheduler.start();
		scheduler.scheduleJobs(triggersAndJobs, true);
	}
	
	// This class must be public.
	public static class MyCronJob implements Job {
		public void execute(JobExecutionContext context) throws JobExecutionException {
			System.out.println(new Date() + " " + MyCronJob.class.getName() + " executed.");
		}
	}
	
}