How to pass instance variables into Quartz job?

While scheduling the job using a trigger, you would have defined JobDataMap that is added to the JobDetail. That JobDetail object will be present in the JobExecutionContext passed to the execute() method in your Job. So, you should figure out a way to pass your externalInstance through the JobDataMap. HTH.

Add the object to the JobDataMap:

JobDetail job = JobBuilder.newJob(MyJobClass.class)
                          .withIdentity("MyIdentity",
                                        "MyGroup")
                          .build();
job.getJobDataMap()
   .put("MyObject",
        myObject);

Access the data from the JobDataMap:

var myObject = (MyObjectClass) context.getJobDetail()
                                      .getJobDataMap()
                                      .get("carrier");

you can put your instance in the schedulerContext.When you are going to schedule the job ,just before that you can do below:

getScheduler().getContext().put("externalInstance", externalInstance);

Your job class would be like below:

public class SimpleJob implements Job {
    @Override
    public void execute(JobExecutionContext context)
            throws JobExecutionException {
        SchedulerContext schedulerContext = null;
        try {
            schedulerContext = context.getScheduler().getContext();
        } catch (SchedulerException e1) {
            e1.printStackTrace();
        }
        ExternalInstance externalInstance =
            (ExternalInstance) schedulerContext.get("externalInstance");

        float avg = externalInstance.calculateAvg();
    }
}

If you are using Spring ,you can actually using spring's support to inject the whole applicationContext like answered in the Link