docs: public void cleanup () {
          //==========================================================================//
          //================= Cancel/Terminate Your Spot Request =====================//
          //==========================================================================//
          try {
              // Cancel requests.
              System.out.println("Cancelling requests.");
              CancelSpotInstanceRequestsRequest cancelRequest = new CancelSpotInstanceRequestsRequest(spotInstanceRequestIds);
              ec2.cancelSpotInstanceRequests(cancelRequest);
          } catch (AmazonServiceException e) {
              // Write out any exceptions that may have occurred.
              System.out.println("Error cancelling instances");
              System.out.println("Caught Exception: " + e.getMessage());
              System.out.println("Reponse Status Code: " + e.getStatusCode());
              System.out.println("Error Code: " + e.getErrorCode());
              System.out.println("Request ID: " + e.getRequestId());
          }
  
          try {
              // Terminate instances.
              System.out.println("Terminate instances");
              TerminateInstancesRequest terminateRequest = new TerminateInstancesRequest(instanceIds);
              ec2.terminateInstances(terminateRequest);
          } catch (AmazonServiceException e) {
              // Write out any exceptions that may have occurred.
              System.out.println("Error terminating instances");
              System.out.println("Caught Exception: " + e.getMessage());
              System.out.println("Reponse Status Code: " + e.getStatusCode());
              System.out.println("Error Code: " + e.getErrorCode());
              System.out.println("Request ID: " + e.getRequestId());
          }
  
          // Delete all requests and instances that we have terminated.
          instanceIds.clear();
          spotInstanceRequestIds.clear();
      }