$route = new Route(
        "/{entity}/5/xyz/print",
        array(
          '_controller' => 'Drupal\xyz\Controller\xyzController::demo1',
          '_title' => 'xyz',
        ),
        array(

          '_permission' => 'access content',
        )
      );

      $collection->add('xyz.show_format.' . $entity_type, $route);

//till here exists in routesubscriber.php

public function demo1($entity) {
return array(
      '#markup' => t('hello World!'),
    );
 }
//content of controller