$items['user'] = array(
    'title' => 'User account',
    'title callback' => 'user_menu_title',
    'weight' => -10,
    'route_name' => 'user_page',
    'menu_name' => 'account',
  );

user_page:
  pattern: '/user'
  defaults:
    _content: 'DrupaluserControllerUserController::userPage'
  requirements:
    _access: 'TRUE'

// Alter the menu as defined in modules, keys are like user/%user.
  drupal_alter('menu', $callbacks);
  foreach ($callbacks as $path => $router_item) {
    // If the menu item is a default local task and incorrectly references a
    // route, remove it.
    // @todo This may be removed later depending on the outcome of
    // http://drupal.org/node/1889790
    if (isset($router_item['type']) && $router_item['type'] == MENU_DEFAULT_LOCAL_TASK) {
      unset($callbacks[$path]['route_name']);
    }
    // If the menu item references a route, normalize the route information
    // into the old structure. Note that routes are keyed by name, not path,
    // so the path of the route takes precedence.
    if (isset($router_item['route_name'])) {
      $router_item['page callback'] = 'USES_ROUTE';
      $router_item['access callback'] = TRUE;
      $new_path = _menu_router_translate_route($router_item['route_name']);

      unset($callbacks[$path]);
      $callbacks[$new_path] = $router_item;
    }
  }

<?php
/**
 * @file
 * Contains Drupalua_sc_moduleRoutingSearchAlterRouteSubscriber.
 */

namespace Drupalua_sc_moduleRouting;

use DrupalCoreRoutingRouteSubscriberBase;
use SymfonyComponentRoutingRouteCollection;

/**
 * Listens to the dynamic route events.
 */
class SearchAlterRouteSubscriber extends RouteSubscriberBase {

  /**
   * {@inheritdoc}
   */
  public function alterRoutes(RouteCollection $collection) {
    // Remove the /search route.
    $collection->remove('search.view');
  }

}

<?php

  use DrupalCoreRoutingRouteBuildEvent;
  use DrupalCoreRoutingRoutingEvents;
  use SymfonyComponentEventDispatcherEventSubscriberInterface;

  class RouteSubscriber implements EventSubscriberInterface {

   /**
    * {@inheritdoc}
    */
   public static function getSubscribedEvents() {
      $events[RoutingEvents::ALTER] = 'alterRoutes';
     return $events;
   }

  /**
   * Alters existing routes.
   *
   * @param DrupalCoreRoutingRouteBuildEvent $event
   *   The route building event.
   */
  public function alterRoutes(RouteBuildEvent $event) {
    // Fetch the collection which can be altered.
    $collection = $event->getRouteCollection();
    // The event is fired multiple times so ensure that the user_page route
    // is available.
    if ($route = $collection->get('user_page') {
      // As example add a new requirement.
      $route->setRequirement('_role', 'anonymous');
    }
  }

  }

services:
  mymodule.route_subscriber:
    class: DrupalmymoduleRoutingRouteSubscriber
    tags:
      - { name: event_subscriber }

namespace DrupalmymoduleRouting;

use DrupalCoreRoutingRouteSubscriberBase;
use SymfonyComponentRoutingRouteCollection;

/**
 * Listens to the dynamic route events.
 */
class RouteSubscriber extends RouteSubscriberBase {

  /**
   * {@inheritdoc}
   */
  protected function alterRoutes(RouteCollection $collection) {
    // Change path '/user/login' to '/login'.
    if ($route = $collection->get('user.page')) {
      $route->setDefault('_controller', 'DrupalmymoduleControllerUserController::userPage');
    }
  }

}