error occured instantiating job to be executed in Quartz sheduler

Your job class has to be public. Otherwise, the JobBuilder can not read it.

public class myJob implements Job {           
    public void execute(JobExecutionContext context) throws JobExecutionException {
      System.out.println("Hello!  HelloJob is executing.");
    }
}

1. Class should be public class
2. Default constructor should be public