If you change your class to implement StatefulJob instead of Job, Quartz will take care of this for you. From the StatefulJob javadoc:
stateful jobs are not allowed to execute concurrently, which means new triggers that occur before the completion of the execute(xx) method will be delayed.
StatefulJob extends Job and does not add any new methods, so all you need to do to get the behaviour you want is change this:
public class YourJob implements org.quartz.Job {
void execute(JobExecutionContext context) {/*implementation omitted*/}
}
To this:
public class YourJob implements org.quartz.StatefulJob {
void execute(JobExecutionContext context) {/*implementation omitted*/}
}
Couple more options are here