diff --git a/core/includes/common.inc b/core/includes/common.inc
index 658c1b6..a60844e 100644
--- a/core/includes/common.inc
+++ b/core/includes/common.inc
@@ -672,7 +672,7 @@ function filter_xss_bad_protocol($string) {
  * Arbitrary elements may be added using the $args associative array.
  */
 function format_rss_channel($title, $link, $description, $items, $langcode = NULL, $args = array()) {
-  $langcode = $langcode ? $langcode : \Drupal::languageManager()->getCurrentLanguage(Language::TYPE_CONTENT)->id;
+  $langcode = $langcode ? $langcode : \Drupal::languageManager()->getCurrentLanguage(Language::TYPE_CONTENT)->getId();
 
   $output = "<channel>\n";
   $output .= ' <title>' . String::checkPlain($title) . "</title>\n";
@@ -2076,7 +2076,7 @@ function _drupal_add_js($data = NULL, $options = NULL) {
             'currentPath' => $current_path,
             'currentPathIsAdmin' => $current_path_is_admin,
             'isFront' => drupal_is_front_page(),
-            'currentLanguage' => \Drupal::languageManager()->getCurrentLanguage(Language::TYPE_URL)->id,
+            'currentLanguage' => \Drupal::languageManager()->getCurrentLanguage(Language::TYPE_URL)->getId(),
           );
           if (!empty($current_query)) {
             ksort($current_query);
diff --git a/core/includes/form.inc b/core/includes/form.inc
index 54feee0..6cf7e48 100644
--- a/core/includes/form.inc
+++ b/core/includes/form.inc
@@ -1988,7 +1988,7 @@ function form_process_machine_name($element, &$form_state) {
       'machineName' => array(
         '#' . $source['#id'] => $element['#machine_name'],
       ),
-      'langcode' => $language->id,
+      'langcode' => $language->getId(),
     ),
   );
   $element['#attached']['library'][] = 'core/drupal.machine-name';
diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index 52ce316..e83e3e1 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -2099,7 +2099,7 @@ function template_preprocess_page(&$variables) {
   $variables['front_page']        = url();
   $variables['feed_icons']        = drupal_get_feeds();
   $variables['language']          = $language_interface;
-  $variables['language']->dir     = $language_interface->direction ? 'rtl' : 'ltr';
+  $variables['language']->dir     = $language_interface->getDirection() ? 'rtl' : 'ltr';
   $variables['logo']              = theme_get_setting('logo.url');
   $variables['main_menu']         = theme_get_setting('features.main_menu') ? menu_main_menu() : array();
   $variables['secondary_menu']    = theme_get_setting('features.secondary_menu') ? menu_secondary_menu() : array();
@@ -2247,8 +2247,8 @@ function template_preprocess_maintenance_page(&$variables) {
   $variables['html_attributes'] = new Attribute;
 
   // HTML element attributes.
-  $variables['html_attributes']['lang'] = $language_interface->id;
-  $variables['html_attributes']['dir'] = $language_interface->direction ? 'rtl' : 'ltr';
+  $variables['html_attributes']['lang'] = $language_interface->getId();
+  $variables['html_attributes']['dir'] = $language_interface->getDirection() ? 'rtl' : 'ltr';
 
   // Add favicon
   if (theme_get_setting('features.favicon')) {
diff --git a/core/lib/Drupal/Core/Cache/LanguageCacheContext.php b/core/lib/Drupal/Core/Cache/LanguageCacheContext.php
index e2c1bd9..0a3f16c 100644
--- a/core/lib/Drupal/Core/Cache/LanguageCacheContext.php
+++ b/core/lib/Drupal/Core/Cache/LanguageCacheContext.php
@@ -45,7 +45,7 @@ public function getContext() {
     $context_parts = array();
     if ($this->languageManager->isMultilingual()) {
       foreach ($this->languageManager->getLanguageTypes() as $type) {
-        $context_parts[] = $this->languageManager->getCurrentLanguage($type)->id;
+        $context_parts[] = $this->languageManager->getCurrentLanguage($type)->getId();
       }
     }
     return implode(':', $context_parts);
diff --git a/core/lib/Drupal/Core/Datetime/Date.php b/core/lib/Drupal/Core/Datetime/Date.php
index 898a49e..031c2a3 100644
--- a/core/lib/Drupal/Core/Datetime/Date.php
+++ b/core/lib/Drupal/Core/Datetime/Date.php
@@ -130,7 +130,7 @@ public function format($timestamp, $type = 'medium', $format = '', $timezone = N
     }
 
     if (empty($langcode)) {
-      $langcode = $this->languageManager->getCurrentLanguage()->id;
+      $langcode = $this->languageManager->getCurrentLanguage()->getId();
     }
 
     // Create a DrupalDateTime object from the timestamp and timezone.
diff --git a/core/lib/Drupal/Core/Datetime/DrupalDateTime.php b/core/lib/Drupal/Core/Datetime/DrupalDateTime.php
index 2d4be46..ba57e74 100644
--- a/core/lib/Drupal/Core/Datetime/DrupalDateTime.php
+++ b/core/lib/Drupal/Core/Datetime/DrupalDateTime.php
@@ -53,7 +53,7 @@ class DrupalDateTime extends DateTimePlus {
   public function __construct($time = 'now', $timezone = NULL, $settings = array()) {
     // We can set the langcode and country using Drupal values.
     if (!isset($settings['langcode'])) {
-      $settings['langcode'] = \Drupal::languageManager()->getCurrentLanguage()->id;
+      $settings['langcode'] = \Drupal::languageManager()->getCurrentLanguage()->getId();
     }
 
     if (!isset($settings['country'])) {
diff --git a/core/lib/Drupal/Core/Entity/EntityInterface.php b/core/lib/Drupal/Core/Entity/EntityInterface.php
index 90e4699..7ea7b55 100644
--- a/core/lib/Drupal/Core/Entity/EntityInterface.php
+++ b/core/lib/Drupal/Core/Entity/EntityInterface.php
@@ -37,7 +37,7 @@ public function id();
   /**
    * Returns the language of the entity.
    *
-   * @return \Drupal\Core\Language\Language
+   * @return \Drupal\Core\Language\LanguageInterface
    *   The language object.
    */
   public function language();
diff --git a/core/lib/Drupal/Core/Entity/EntityManager.php b/core/lib/Drupal/Core/Entity/EntityManager.php
index 3ea9429..48c5070 100644
--- a/core/lib/Drupal/Core/Entity/EntityManager.php
+++ b/core/lib/Drupal/Core/Entity/EntityManager.php
@@ -157,7 +157,7 @@ public function __construct(\Traversable $namespaces, ContainerInterface $contai
     $this->discovery = new AnnotatedClassDiscovery('Entity', $namespaces, 'Drupal\Core\Entity\Annotation\EntityType');
     $this->discovery = new InfoHookDecorator($this->discovery, 'entity_type_build');
     $this->discovery = new AlterDecorator($this->discovery, 'entity_type');
-    $this->discovery = new CacheDecorator($this->discovery, 'entity_type:' . $this->languageManager->getCurrentLanguage()->id, 'default', Cache::PERMANENT, array('entity_types' => TRUE));
+    $this->discovery = new CacheDecorator($this->discovery, 'entity_type:' . $this->languageManager->getCurrentLanguage()->getId(), 'default', Cache::PERMANENT, array('entity_types' => TRUE));
 
     $this->container = $container;
   }
@@ -314,7 +314,7 @@ public function getBaseFieldDefinitions($entity_type_id) {
     // Check the static cache.
     if (!isset($this->baseFieldDefinitions[$entity_type_id])) {
       // Not prepared, try to load from cache.
-      $cid = 'entity_base_field_definitions:' . $entity_type_id . ':' . $this->languageManager->getCurrentLanguage()->id;
+      $cid = 'entity_base_field_definitions:' . $entity_type_id . ':' . $this->languageManager->getCurrentLanguage()->getId();
       if ($cache = $this->cache->get($cid)) {
         $this->baseFieldDefinitions[$entity_type_id] = $cache->data;
       }
@@ -404,7 +404,7 @@ public function getFieldDefinitions($entity_type_id, $bundle) {
     if (!isset($this->fieldDefinitions[$entity_type_id][$bundle])) {
       $base_field_definitions = $this->getBaseFieldDefinitions($entity_type_id);
       // Not prepared, try to load from cache.
-      $cid = 'entity_bundle_field_definitions:' . $entity_type_id . ':' . $bundle . ':' . $this->languageManager->getCurrentLanguage()->id;
+      $cid = 'entity_bundle_field_definitions:' . $entity_type_id . ':' . $bundle . ':' . $this->languageManager->getCurrentLanguage()->getId();
       if ($cache = $this->cache->get($cid)) {
         $bundle_field_definitions = $cache->data;
       }
@@ -505,7 +505,7 @@ public function getBundleInfo($entity_type) {
    */
   public function getAllBundleInfo() {
     if (!isset($this->bundleInfo)) {
-      $langcode = $this->languageManager->getCurrentLanguage()->id;
+      $langcode = $this->languageManager->getCurrentLanguage()->getId();
       if ($cache = $this->cache->get("entity_bundle_info:$langcode")) {
         $this->bundleInfo = $cache->data;
       }
@@ -537,7 +537,7 @@ public function getExtraFields($entity_type_id, $bundle) {
     // Read from the persistent cache. Since hook_entity_extra_field_info() and
     // hook_entity_extra_field_info_alter() might contain t() calls, we cache
     // per language.
-    $cache_id = 'entity_bundle_extra_fields:' . $entity_type_id . ':' . $bundle . ':' . $this->languageManager->getCurrentLanguage()->id;
+    $cache_id = 'entity_bundle_extra_fields:' . $entity_type_id . ':' . $bundle . ':' . $this->languageManager->getCurrentLanguage()->getId();
     $cached = $this->cache->get($cache_id);
     if ($cached) {
       $this->extraFields[$entity_type_id][$bundle] = $cached->data;
@@ -581,7 +581,7 @@ public function getTranslationFromContext(EntityInterface $entity, $langcode = N
 
     if ($entity instanceof TranslatableInterface) {
       if (empty($langcode)) {
-        $langcode = $this->languageManager->getCurrentLanguage(Language::TYPE_CONTENT)->id;
+        $langcode = $this->languageManager->getCurrentLanguage(Language::TYPE_CONTENT)->getId();
       }
 
       // Retrieve language fallback candidates to perform the entity language
@@ -592,7 +592,7 @@ public function getTranslationFromContext(EntityInterface $entity, $langcode = N
 
       // Ensure the default language has the proper language code.
       $default_language = $entity->getUntranslated()->language();
-      $candidates[$default_language->id] = Language::LANGCODE_DEFAULT;
+      $candidates[$default_language->getId()] = Language::LANGCODE_DEFAULT;
 
       // Return the most fitting entity translation.
       foreach ($candidates as $candidate) {
@@ -646,7 +646,7 @@ public function getFormModes($entity_type_id) {
   protected function getAllDisplayModesByEntityType($display_type) {
     if (!isset($this->displayModeInfo[$display_type])) {
       $key = 'entity_' . $display_type . '_info';
-      $langcode = $this->languageManager->getCurrentLanguage(Language::TYPE_INTERFACE)->id;
+      $langcode = $this->languageManager->getCurrentLanguage(Language::TYPE_INTERFACE)->getId();
       if ($cache = $this->cache->get("$key:$langcode")) {
         $this->displayModeInfo[$display_type] = $cache->data;
       }
diff --git a/core/lib/Drupal/Core/Entity/EntityViewBuilder.php b/core/lib/Drupal/Core/Entity/EntityViewBuilder.php
index b4c72a4..16d7a09 100644
--- a/core/lib/Drupal/Core/Entity/EntityViewBuilder.php
+++ b/core/lib/Drupal/Core/Entity/EntityViewBuilder.php
@@ -205,7 +205,7 @@ public function view(EntityInterface $entity, $view_mode = 'full', $langcode = N
    */
   public function viewMultiple(array $entities = array(), $view_mode = 'full', $langcode = NULL) {
     if (!isset($langcode)) {
-      $langcode = $this->languageManager->getCurrentLanguage(Language::TYPE_CONTENT)->id;
+      $langcode = $this->languageManager->getCurrentLanguage(Language::TYPE_CONTENT)->getId();
     }
 
     // Build the view modes and display objects.
diff --git a/core/lib/Drupal/Core/EventSubscriber/FinishResponseSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/FinishResponseSubscriber.php
index 8e4596f..0576520 100644
--- a/core/lib/Drupal/Core/EventSubscriber/FinishResponseSubscriber.php
+++ b/core/lib/Drupal/Core/EventSubscriber/FinishResponseSubscriber.php
@@ -55,7 +55,7 @@ public function onRespond(FilterResponseEvent $event) {
     $response->headers->set('X-UA-Compatible', 'IE=edge,chrome=1', FALSE);
 
     // Set the Content-language header.
-    $response->headers->set('Content-language', $this->languageManager->getCurrentLanguage()->id);
+    $response->headers->set('Content-language', $this->languageManager->getCurrentLanguage()->getId());
 
     // Because pages are highly dynamic, set the last-modified time to now
     // since the page is in fact being regenerated right now.
diff --git a/core/lib/Drupal/Core/Language/Language.php b/core/lib/Drupal/Core/Language/Language.php
index 4575983..1a9755e 100644
--- a/core/lib/Drupal/Core/Language/Language.php
+++ b/core/lib/Drupal/Core/Language/Language.php
@@ -35,14 +35,14 @@ class Language implements LanguageInterface {
    *
    * @var string
    */
-  public $name = '';
+  protected $name = '';
 
   /**
    * The ID, langcode.
    *
    * @var string
    */
-  public $id = '';
+  protected $id = '';
 
   /**
    * The direction, left-to-right, or right-to-left.
@@ -51,21 +51,21 @@ class Language implements LanguageInterface {
    *
    * @var int
    */
-  public $direction = self::DIRECTION_LTR;
+  protected $direction = self::DIRECTION_LTR;
 
   /**
    * The weight, used for ordering languages in lists, like selects or tables.
    *
    * @var int
    */
-  public $weight = 0;
+  protected $weight = 0;
 
   /**
    * Flag indicating if this is the only site default language.
    *
    * @var bool
    */
-  public $default = FALSE;
+  protected $default = FALSE;
 
   /**
    * The language negotiation method used when a language was detected.
@@ -75,7 +75,7 @@ class Language implements LanguageInterface {
    *
    * @var string
    */
-  public $method_id;
+  protected $negotiationMethodId;
 
   /**
    * Locked indicates a language used by the system, not an actual language.
@@ -86,7 +86,7 @@ class Language implements LanguageInterface {
    *
    * @var bool
    */
-  public $locked = FALSE;
+  protected $locked = FALSE;
 
   /**
    * Constructs a new class instance.
@@ -197,14 +197,14 @@ public function setDefault($default) {
    * {@inheritdoc}
    */
   public function getNegotiationMethodId() {
-    return $this->method_id;
+    return $this->negotiationMethodId;
   }
 
   /**
    * {@inheritdoc}
    */
   public function setNegotiationMethodId($method_id) {
-    $this->method_id = $method_id;
+    $this->negotiationMethodId = $method_id;
 
     return $this;
   }
diff --git a/core/lib/Drupal/Core/Path/AliasManager.php b/core/lib/Drupal/Core/Path/AliasManager.php
index 84dbb02..448be88 100644
--- a/core/lib/Drupal/Core/Path/AliasManager.php
+++ b/core/lib/Drupal/Core/Path/AliasManager.php
@@ -95,7 +95,7 @@ public function getSystemPath($path, $path_language = NULL) {
     // language. If we used a language different from the one conveyed by the
     // requested URL, we might end up being unable to check if there is a path
     // alias matching the URL path.
-    $path_language = $path_language ?: $this->languageManager->getCurrentLanguage(Language::TYPE_URL)->id;
+    $path_language = $path_language ?: $this->languageManager->getCurrentLanguage(Language::TYPE_URL)->getId();
     // Lookup the path alias first.
     if (!empty($path) && $source = $this->lookupPathSource($path, $path_language)) {
       $path = $source;
@@ -112,7 +112,7 @@ public function getPathAlias($path, $path_language = NULL) {
     // language. If we used a language different from the one conveyed by the
     // requested URL, we might end up being unable to check if there is a path
     // alias matching the URL path.
-    $path_language = $path_language ?: $this->languageManager->getCurrentLanguage(Language::TYPE_URL)->id;
+    $path_language = $path_language ?: $this->languageManager->getCurrentLanguage(Language::TYPE_URL)->getId();
     $result = $path;
     if (!empty($path) && $alias = $this->lookupPathAlias($path, $path_language)) {
       $result = $alias;
diff --git a/core/lib/Drupal/Core/Plugin/DefaultPluginManager.php b/core/lib/Drupal/Core/Plugin/DefaultPluginManager.php
index e9c4ce9..f79949d 100644
--- a/core/lib/Drupal/Core/Plugin/DefaultPluginManager.php
+++ b/core/lib/Drupal/Core/Plugin/DefaultPluginManager.php
@@ -146,7 +146,7 @@ public function setCacheBackend(CacheBackendInterface $cache_backend, LanguageMa
     $this->languageManager = $language_manager;
     $this->cacheBackend = $cache_backend;
     $this->cacheKeyPrefix = $cache_key_prefix;
-    $this->cacheKey = $cache_key_prefix . ':' . $language_manager->getCurrentLanguage()->id;
+    $this->cacheKey = $cache_key_prefix . ':' . $language_manager->getCurrentLanguage()->getId();
     $this->cacheTags = $cache_tags;
   }
 
diff --git a/core/lib/Drupal/Core/Validation/DrupalTranslator.php b/core/lib/Drupal/Core/Validation/DrupalTranslator.php
index 5b4d99d..8247e13 100644
--- a/core/lib/Drupal/Core/Validation/DrupalTranslator.php
+++ b/core/lib/Drupal/Core/Validation/DrupalTranslator.php
@@ -56,7 +56,7 @@ public function setLocale($locale) {
    * Implements \Symfony\Component\Translation\TranslatorInterface::getLocale().
    */
   public function getLocale() {
-    return $this->locale ? $this->locale : \Drupal::languageManager()->getCurrentLanguage()->id;
+    return $this->locale ? $this->locale : \Drupal::languageManager()->getCurrentLanguage()->getId();
   }
 
   /**
diff --git a/core/modules/block/custom_block/lib/Drupal/custom_block/CustomBlockFormController.php b/core/modules/block/custom_block/lib/Drupal/custom_block/CustomBlockFormController.php
index 73d1adc..cba823e 100644
--- a/core/modules/block/custom_block/lib/Drupal/custom_block/CustomBlockFormController.php
+++ b/core/modules/block/custom_block/lib/Drupal/custom_block/CustomBlockFormController.php
@@ -102,7 +102,7 @@ public function form(array $form, array &$form_state) {
       // Set the correct default language.
       if ($block->isNew()) {
         $language_default = $this->languageManager->getCurrentLanguage($language_configuration['langcode']);
-        $block->langcode->value = $language_default->id;
+        $block->langcode->value = $language_default->getId();
       }
     }
 
diff --git a/core/modules/block/lib/Drupal/block/BlockAccessController.php b/core/modules/block/lib/Drupal/block/BlockAccessController.php
index 4f5182b..3e05566 100644
--- a/core/modules/block/lib/Drupal/block/BlockAccessController.php
+++ b/core/modules/block/lib/Drupal/block/BlockAccessController.php
@@ -117,7 +117,7 @@ protected function checkAccess(EntityInterface $entity, $operation, $langcode, A
 
     // Language visibility settings.
     if (!empty($visibility['language']['langcodes']) && array_filter($visibility['language']['langcodes'])) {
-      if (empty($visibility['language']['langcodes'][\Drupal::languageManager()->getCurrentLanguage($visibility['language']['language_type'])->id])) {
+      if (empty($visibility['language']['langcodes'][\Drupal::languageManager()->getCurrentLanguage($visibility['language']['language_type'])->getId()])) {
         return FALSE;
       }
     }
diff --git a/core/modules/book/book.module b/core/modules/book/book.module
index 8c52221..24857e0 100644
--- a/core/modules/book/book.module
+++ b/core/modules/book/book.module
@@ -488,13 +488,13 @@ function template_preprocess_book_export_html(&$variables) {
   $variables['title'] = String::checkPlain($variables['title']);
   $variables['base_url'] = $base_url;
   $variables['language'] = $language_interface;
-  $variables['language_rtl'] = ($language_interface->direction == Language::DIRECTION_RTL);
+  $variables['language_rtl'] = ($language_interface->getDirection() == Language::DIRECTION_RTL);
   $variables['head'] = drupal_get_html_head();
 
   // HTML element attributes.
   $attributes = array();
-  $attributes['lang'] = $language_interface->id;
-  $attributes['dir'] = $language_interface->direction ? 'rtl' : 'ltr';
+  $attributes['lang'] = $language_interface->getId();
+  $attributes['dir'] = $language_interface->getDirection() ? 'rtl' : 'ltr';
   $variables['html_attributes'] = new Attribute($attributes);
 }
 
diff --git a/core/modules/book/lib/Drupal/book/BookManager.php b/core/modules/book/lib/Drupal/book/BookManager.php
index 3e0a6aa..49e904c 100644
--- a/core/modules/book/lib/Drupal/book/BookManager.php
+++ b/core/modules/book/lib/Drupal/book/BookManager.php
@@ -479,7 +479,7 @@ public function bookTreeAllData($bid, $link = NULL, $max_depth = NULL) {
     $nid = isset($link['nid']) ? $link['nid'] : 0;
     // Generate a cache ID (cid) specific for this $bid, $link, $language, and
     // depth.
-    $cid = 'book-links:' . $bid . ':all:' . $nid . ':' . $language_interface->id . ':' . (int) $max_depth;
+    $cid = 'book-links:' . $bid . ':all:' . $nid . ':' . $language_interface->getId() . ':' . (int) $max_depth;
 
     if (!isset($tree[$cid])) {
       // If the tree data was not in the static cache, build $tree_parameters.
@@ -632,7 +632,7 @@ protected function doBookTreeBuild($bid, array $parameters = array()) {
     if (isset($parameters['expanded'])) {
       sort($parameters['expanded']);
     }
-    $tree_cid = 'book-links:' . $bid . ':tree-data:' . $language_interface->id . ':' . hash('sha256', serialize($parameters));
+    $tree_cid = 'book-links:' . $bid . ':tree-data:' . $language_interface->getId() . ':' . hash('sha256', serialize($parameters));
 
     // If we do not have this tree in the static cache, check {cache_data}.
     if (!isset($trees[$tree_cid])) {
diff --git a/core/modules/ckeditor/ckeditor.admin.inc b/core/modules/ckeditor/ckeditor.admin.inc
index 7d763c7..8636093 100644
--- a/core/modules/ckeditor/ckeditor.admin.inc
+++ b/core/modules/ckeditor/ckeditor.admin.inc
@@ -21,7 +21,7 @@
 function template_preprocess_ckeditor_settings_toolbar(&$variables) {
   // Simplify the language direction information for toolbar buttons.
   $language_interface = \Drupal::languageManager()->getCurrentLanguage();
-  $language_direction = $language_interface->direction ? 'rtl' : 'ltr';
+  $language_direction = $language_interface->getDirection() ? 'rtl' : 'ltr';
 
   // Create lists of active and disabled buttons.
   $editor = $variables['editor'];
diff --git a/core/modules/ckeditor/lib/Drupal/ckeditor/Plugin/Editor/CKEditor.php b/core/modules/ckeditor/lib/Drupal/ckeditor/Plugin/Editor/CKEditor.php
index f248e22..f8618ce 100644
--- a/core/modules/ckeditor/lib/Drupal/ckeditor/Plugin/Editor/CKEditor.php
+++ b/core/modules/ckeditor/lib/Drupal/ckeditor/Plugin/Editor/CKEditor.php
@@ -269,8 +269,8 @@ public function getJSSettings(EditorEntity $editor) {
     // Map the interface language code to a CKEditor translation.
     $ckeditor_langcodes = $this->getLangcodes();
     $language_interface = $this->languageManager->getCurrentLanguage();
-    if (isset($ckeditor_langcodes[$language_interface->id])) {
-      $display_langcode = $ckeditor_langcodes[$language_interface->id];
+    if (isset($ckeditor_langcodes[$language_interface->getId()])) {
+      $display_langcode = $ckeditor_langcodes[$language_interface->getId()];
     }
 
     // Next, set the most fundamental CKEditor settings.
diff --git a/core/modules/comment/lib/Drupal/comment/CommentFormController.php b/core/modules/comment/lib/Drupal/comment/CommentFormController.php
index e9759eb..063a7b7 100644
--- a/core/modules/comment/lib/Drupal/comment/CommentFormController.php
+++ b/core/modules/comment/lib/Drupal/comment/CommentFormController.php
@@ -75,7 +75,7 @@ protected function init(array &$form_state) {
     // set.
     if ($comment->isNew()) {
       $language_content = \Drupal::languageManager()->getCurrentLanguage(Language::TYPE_CONTENT);
-      $comment->langcode->value = $language_content->id;
+      $comment->langcode->value = $language_content->getId();
     }
 
     parent::init($form_state);
diff --git a/core/modules/comment/lib/Drupal/comment/Tests/CommentTokenReplaceTest.php b/core/modules/comment/lib/Drupal/comment/Tests/CommentTokenReplaceTest.php
index 0d2a4b2..9523e43 100644
--- a/core/modules/comment/lib/Drupal/comment/Tests/CommentTokenReplaceTest.php
+++ b/core/modules/comment/lib/Drupal/comment/Tests/CommentTokenReplaceTest.php
@@ -63,8 +63,8 @@ function testCommentTokenReplacement() {
     $tests['[comment:body]'] = $comment->comment_body->processed;
     $tests['[comment:url]'] = url('comment/' . $comment->id(), $url_options + array('fragment' => 'comment-' . $comment->id()));
     $tests['[comment:edit-url]'] = url('comment/' . $comment->id() . '/edit', $url_options);
-    $tests['[comment:created:since]'] = format_interval(REQUEST_TIME - $comment->getCreatedTime(), 2, $language_interface->id);
-    $tests['[comment:changed:since]'] = format_interval(REQUEST_TIME - $comment->getChangedTime(), 2, $language_interface->id);
+    $tests['[comment:created:since]'] = format_interval(REQUEST_TIME - $comment->getCreatedTime(), 2, $language_interface->getId());
+    $tests['[comment:changed:since]'] = format_interval(REQUEST_TIME - $comment->getChangedTime(), 2, $language_interface->getId());
     $tests['[comment:parent:cid]'] = $comment->hasParentComment() ? $comment->getParentComment()->id() : NULL;
     $tests['[comment:parent:title]'] = check_plain($parent_comment->getSubject());
     $tests['[comment:node:nid]'] = $comment->getCommentedEntityId();
@@ -76,7 +76,7 @@ function testCommentTokenReplacement() {
     $this->assertFalse(in_array(0, array_map('strlen', $tests)), 'No empty tokens generated.');
 
     foreach ($tests as $input => $expected) {
-      $output = $token_service->replace($input, array('comment' => $comment), array('langcode' => $language_interface->id));
+      $output = $token_service->replace($input, array('comment' => $comment), array('langcode' => $language_interface->getId()));
       $this->assertEqual($output, $expected, format_string('Sanitized comment token %token replaced.', array('%token' => $input)));
     }
 
@@ -93,7 +93,7 @@ function testCommentTokenReplacement() {
     $tests['[comment:author:name]'] = $this->admin_user->getUsername();
 
     foreach ($tests as $input => $expected) {
-      $output = $token_service->replace($input, array('comment' => $comment), array('langcode' => $language_interface->id, 'sanitize' => FALSE));
+      $output = $token_service->replace($input, array('comment' => $comment), array('langcode' => $language_interface->getId(), 'sanitize' => FALSE));
       $this->assertEqual($output, $expected, format_string('Unsanitized comment token %token replaced.', array('%token' => $input)));
     }
 
@@ -108,7 +108,7 @@ function testCommentTokenReplacement() {
     $tests['[node:comment-count]'] = 2;
 
     foreach ($tests as $input => $expected) {
-      $output = $token_service->replace($input, array('entity' => $node, 'node' => $node), array('langcode' => $language_interface->id));
+      $output = $token_service->replace($input, array('entity' => $node, 'node' => $node), array('langcode' => $language_interface->getId()));
       $this->assertEqual($output, $expected, format_string('Node comment token %token replaced.', array('%token' => $input)));
     }
   }
diff --git a/core/modules/contact/lib/Drupal/contact/MessageFormController.php b/core/modules/contact/lib/Drupal/contact/MessageFormController.php
index 2058887..22e2b71 100644
--- a/core/modules/contact/lib/Drupal/contact/MessageFormController.php
+++ b/core/modules/contact/lib/Drupal/contact/MessageFormController.php
@@ -213,7 +213,7 @@ public function save(array $form, array &$form_state) {
       $params['contact_category'] = $category;
 
       $to = implode(', ', $category->recipients);
-      $recipient_langcode = language_default()->id;
+      $recipient_langcode = language_default()->getId();
     }
     elseif ($recipient = $message->getPersonalRecipient()) {
       // Send to the user in the user's preferred language.
@@ -231,14 +231,14 @@ public function save(array $form, array &$form_state) {
 
     // If requested, send a copy to the user, using the current language.
     if ($message->copySender()) {
-      drupal_mail('contact', $key_prefix . '_copy', $sender->getEmail(), $language_interface->id, $params, $sender->getEmail());
+      drupal_mail('contact', $key_prefix . '_copy', $sender->getEmail(), $language_interface->getId(), $params, $sender->getEmail());
     }
 
     // If configured, send an auto-reply, using the current language.
     if (!$message->isPersonal() && $category->reply) {
       // User contact forms do not support an auto-reply message, so this
       // message always originates from the site.
-      drupal_mail('contact', 'page_autoreply', $sender->getEmail(), $language_interface->id, $params);
+      drupal_mail('contact', 'page_autoreply', $sender->getEmail(), $language_interface->getId(), $params);
     }
 
     $config = $this->configFactory->get('contact.settings');
diff --git a/core/modules/content_translation/content_translation.pages.inc b/core/modules/content_translation/content_translation.pages.inc
index 16864bf..0fd3edc 100644
--- a/core/modules/content_translation/content_translation.pages.inc
+++ b/core/modules/content_translation/content_translation.pages.inc
@@ -110,7 +110,7 @@ function content_translation_overview(EntityInterface $entity) {
       else {
         // No such translation in the set yet: help user to create it.
         $row_title = $source_name = t('n/a');
-        $source = $entity->language()->id;
+        $source = $entity->language()->getId();
 
         if ($source != $langcode && $controller->getTranslationAccess($entity, 'create')) {
           if ($translatable) {
@@ -187,7 +187,7 @@ function content_translation_add_page(EntityInterface $entity, Language $source
   $target = !empty($target) ? $target : \Drupal::languageManager()->getCurrentLanguage(Language::TYPE_CONTENT);
   // @todo Exploit the upcoming hook_entity_prepare() when available.
   content_translation_prepare_translation($entity, $source, $target);
-  $form_state['langcode'] = $target->id;
+  $form_state['langcode'] = $target->getId();
   $form_state['content_translation']['source'] = $source;
   $form_state['content_translation']['target'] = $target;
   $form_state['content_translation']['translation_form'] = !$entity->access('update');
@@ -211,7 +211,7 @@ function content_translation_add_page(EntityInterface $entity, Language $source
  */
 function content_translation_edit_page(EntityInterface $entity, Language $language = NULL) {
   $language = !empty($language) ? $language : \Drupal::languageManager()->getCurrentLanguage(Language::TYPE_CONTENT);
-  $form_state['langcode'] = $language->id;
+  $form_state['langcode'] = $language->getId();
   $form_state['content_translation']['translation_form'] = TRUE;
   return \Drupal::service('entity.form_builder')->getForm($entity, 'default', $form_state);
 }
@@ -228,7 +228,7 @@ function content_translation_edit_page(EntityInterface $entity, Language $langua
  */
 function content_translation_prepare_translation(EntityInterface $entity, Language $source, Language $target) {
   if ($entity instanceof ContentEntityInterface) {
-    $source_translation = $entity->getTranslation($source->id);
-    $entity->addTranslation($target->id, $source_translation->toArray());
+    $source_translation = $entity->getTranslation($source->getId());
+    $entity->addTranslation($target->getId(), $source_translation->toArray());
   }
 }
diff --git a/core/modules/content_translation/lib/Drupal/content_translation/Access/ContentTranslationManageAccessCheck.php b/core/modules/content_translation/lib/Drupal/content_translation/Access/ContentTranslationManageAccessCheck.php
index b9b4904..8e3a81b 100644
--- a/core/modules/content_translation/lib/Drupal/content_translation/Access/ContentTranslationManageAccessCheck.php
+++ b/core/modules/content_translation/lib/Drupal/content_translation/Access/ContentTranslationManageAccessCheck.php
@@ -57,10 +57,10 @@ public function access(Route $route, Request $request, AccountInterface $account
           $target = language_load($request->attributes->get('target'));
           $source = !empty($source) ? $source : $entity->language();
           $target = !empty($target) ? $target : \Drupal::languageManager()->getCurrentLanguage(Language::TYPE_CONTENT);
-          return ($source->id != $target->id
-            && isset($languages[$source->id])
-            && isset($languages[$target->id])
-            && !isset($translations[$target->id])
+          return ($source->getId() != $target->getId()
+            && isset($languages[$source->getId()])
+            && isset($languages[$target->getId()])
+            && !isset($translations[$target->getId()])
             && $controller->getTranslationAccess($entity, $operation))
             ? static::ALLOW : static::DENY;
 
@@ -68,9 +68,9 @@ public function access(Route $route, Request $request, AccountInterface $account
         case 'delete':
           $language = language_load($request->attributes->get('language'));
           $language = !empty($language) ? $language : \Drupal::languageManager()->getCurrentLanguage(Language::TYPE_CONTENT);
-          return isset($languages[$language->id])
-            && $language->id != $entity->getUntranslated()->language()->id
-            && isset($translations[$language->id])
+          return isset($languages[$language->getId()])
+            && $language->getId() != $entity->getUntranslated()->language()->id
+            && isset($translations[$language->getId()])
             && $controller->getTranslationAccess($entity, $operation)
             ? static::ALLOW : static::DENY;
       }
diff --git a/core/modules/field/lib/Drupal/field/Plugin/views/field/Field.php b/core/modules/field/lib/Drupal/field/Plugin/views/field/Field.php
index 2628dfa..788239c 100644
--- a/core/modules/field/lib/Drupal/field/Plugin/views/field/Field.php
+++ b/core/modules/field/lib/Drupal/field/Plugin/views/field/Field.php
@@ -255,7 +255,7 @@ public function query($use_groupby = FALSE) {
         $column = $this->tableAlias . '.langcode';
         // By the same reason as field_language the field might be Language::LANGCODE_NOT_SPECIFIED in reality so allow it as well.
         // @see this::field_langcode()
-        $default_langcode = language_default()->id;
+        $default_langcode = language_default()->getId();
         $langcode = str_replace(
           array('***CURRENT_LANGUAGE***', '***DEFAULT_LANGUAGE***'),
           array($this->languageManager->getCurrentLanguage(Language::TYPE_CONTENT), $default_langcode),
@@ -861,7 +861,7 @@ protected function addSelfTokens(&$tokens, $item) {
    */
   function field_langcode(EntityInterface $entity) {
     if ($this->field_info->isTranslatable()) {
-      $default_langcode = language_default()->id;
+      $default_langcode = language_default()->getId();
       $langcode = str_replace(
         array('***CURRENT_LANGUAGE***', '***DEFAULT_LANGUAGE***'),
         array($this->languageManager->getCurrentLanguage(Language::TYPE_CONTENT), $default_langcode),
@@ -873,7 +873,7 @@ function field_langcode(EntityInterface $entity) {
       // for the selected language. FieldItemListInterface::view() does this as
       // well, but since the returned language code is used before calling it,
       // the fallback needs to happen explicitly.
-      $langcode = $this->entityManager->getTranslationFromContext($entity, $langcode)->language()->id;
+      $langcode = $this->entityManager->getTranslationFromContext($entity, $langcode)->language()->getId();
 
       return $langcode;
     }
diff --git a/core/modules/file/lib/Drupal/file/Tests/FileTokenReplaceTest.php b/core/modules/file/lib/Drupal/file/Tests/FileTokenReplaceTest.php
index 35bb593..4474dd9 100644
--- a/core/modules/file/lib/Drupal/file/Tests/FileTokenReplaceTest.php
+++ b/core/modules/file/lib/Drupal/file/Tests/FileTokenReplaceTest.php
@@ -53,10 +53,10 @@ function testFileTokenReplacement() {
     $tests['[file:mime]'] = check_plain($file->getMimeType());
     $tests['[file:size]'] = format_size($file->getSize());
     $tests['[file:url]'] = check_plain(file_create_url($file->getFileUri()));
-    $tests['[file:created]'] = format_date($file->getCreatedTime(), 'medium', '', NULL, $language_interface->id);
-    $tests['[file:created:short]'] = format_date($file->getCreatedTime(), 'short', '', NULL, $language_interface->id);
-    $tests['[file:changed]'] = format_date($file->getChangedTime(), 'medium', '', NULL, $language_interface->id);
-    $tests['[file:changed:short]'] = format_date($file->getChangedTime(), 'short', '', NULL, $language_interface->id);
+    $tests['[file:created]'] = format_date($file->getCreatedTime(), 'medium', '', NULL, $language_interface->getId());
+    $tests['[file:created:short]'] = format_date($file->getCreatedTime(), 'short', '', NULL, $language_interface->getId());
+    $tests['[file:changed]'] = format_date($file->getChangedTime(), 'medium', '', NULL, $language_interface->getId());
+    $tests['[file:changed:short]'] = format_date($file->getChangedTime(), 'short', '', NULL, $language_interface->getId());
     $tests['[file:owner]'] = check_plain(user_format_name($this->admin_user));
     $tests['[file:owner:uid]'] = $file->getOwnerId();
 
@@ -64,7 +64,7 @@ function testFileTokenReplacement() {
     $this->assertFalse(in_array(0, array_map('strlen', $tests)), 'No empty tokens generated.');
 
     foreach ($tests as $input => $expected) {
-      $output = $token_service->replace($input, array('file' => $file), array('langcode' => $language_interface->id));
+      $output = $token_service->replace($input, array('file' => $file), array('langcode' => $language_interface->getId()));
       $this->assertEqual($output, $expected, format_string('Sanitized file token %token replaced.', array('%token' => $input)));
     }
 
@@ -75,7 +75,7 @@ function testFileTokenReplacement() {
     $tests['[file:size]'] = format_size($file->getSize());
 
     foreach ($tests as $input => $expected) {
-      $output = $token_service->replace($input, array('file' => $file), array('langcode' => $language_interface->id, 'sanitize' => FALSE));
+      $output = $token_service->replace($input, array('file' => $file), array('langcode' => $language_interface->getId(), 'sanitize' => FALSE));
       $this->assertEqual($output, $expected, format_string('Unsanitized file token %token replaced.', array('%token' => $input)));
     }
   }
diff --git a/core/modules/filter/filter.module b/core/modules/filter/filter.module
index 2e71d68..4098b35 100644
--- a/core/modules/filter/filter.module
+++ b/core/modules/filter/filter.module
@@ -142,13 +142,13 @@ function filter_formats(AccountInterface $account = NULL) {
   // All available formats are cached for performance.
   if (!isset($formats['all'])) {
     $language_interface = \Drupal::languageManager()->getCurrentLanguage();
-    if ($cache = \Drupal::cache()->get("filter_formats:{$language_interface->id}")) {
+    if ($cache = \Drupal::cache()->get("filter_formats:{$language_interface->getId()}")) {
       $formats['all'] = $cache->data;
     }
     else {
       $formats['all'] = \Drupal::entityManager()->getStorage('filter_format')->loadByProperties(array('status' => TRUE));
       uasort($formats['all'], 'Drupal\Core\Config\Entity\ConfigEntityBase::sort');
-      \Drupal::cache()->set("filter_formats:{$language_interface->id}", $formats['all'], Cache::PERMANENT, array('filter_formats' => TRUE));
+      \Drupal::cache()->set("filter_formats:{$language_interface->getId()}", $formats['all'], Cache::PERMANENT, array('filter_formats' => TRUE));
     }
   }
 
diff --git a/core/modules/language/language.module b/core/modules/language/language.module
index 71db626..5cb9cd8 100644
--- a/core/modules/language/language.module
+++ b/core/modules/language/language.module
@@ -203,7 +203,7 @@ function language_element_info() {
  */
 function language_configuration_element_default_options() {
   $language_options = array(
-    'site_default' => t("Site's default language (!language)", array('!language' => \Drupal::languageManager()->getDefaultLanguage()->name)),
+    'site_default' => t("Site's default language (!language)", array('!language' => \Drupal::languageManager()->getDefaultLanguage()->getName())),
     'current_interface' => t('Current interface language'),
     'authors_default' => t("Author's preferred language"),
   );
@@ -383,11 +383,11 @@ function language_get_default_langcode($entity_type, $bundle) {
   $language_interface = \Drupal::languageManager()->getCurrentLanguage();
   switch ($configuration['langcode']) {
     case 'site_default':
-      $default_value = \Drupal::languageManager()->getDefaultLanguage()->id;
+      $default_value = \Drupal::languageManager()->getDefaultLanguage()->getId();
       break;
 
     case 'current_interface':
-      $default_value = $language_interface->id;
+      $default_value = $language_interface->getId();
       break;
 
     case 'authors_default':
@@ -397,7 +397,7 @@ function language_get_default_langcode($entity_type, $bundle) {
         $default_value = $language_code;
       }
       else {
-        $default_value = $language_interface->id;
+        $default_value = $language_interface->getId();
       }
       break;
   }
@@ -688,7 +688,7 @@ function language_form_system_regional_settings_alter(&$form, &$form_state) {
   $form['locale']['site_default_language'] = array(
     '#type' => 'select',
     '#title' => t('Default language'),
-    '#default_value' => $default->id,
+    '#default_value' => $default->getId(),
     '#options' => $language_options,
     '#description' => t('It is not recommended to change the default language on a working site. <a href="@language-detection">Configure the Selected language</a> setting on the detection and selection page to change the fallback language for language selection.', array('@language-detection' => url('admin/config/regional/language/detection'))),
     '#weight' => -1,
diff --git a/core/modules/language/lib/Drupal/language/EventSubscriber/LanguageRequestSubscriber.php b/core/modules/language/lib/Drupal/language/EventSubscriber/LanguageRequestSubscriber.php
index 7700611..fcbd232 100644
--- a/core/modules/language/lib/Drupal/language/EventSubscriber/LanguageRequestSubscriber.php
+++ b/core/modules/language/lib/Drupal/language/EventSubscriber/LanguageRequestSubscriber.php
@@ -86,7 +86,7 @@ public function onKernelRequestLanguage(GetResponseEvent $event) {
       }
       // After the language manager has initialized, set the default langcode
       // for the string translations.
-      $langcode = $this->languageManager->getCurrentLanguage()->id;
+      $langcode = $this->languageManager->getCurrentLanguage()->getId();
       $this->translation->setDefaultLangcode($langcode);
     }
   }
diff --git a/core/modules/language/lib/Drupal/language/LanguageNegotiationMethodBase.php b/core/modules/language/lib/Drupal/language/LanguageNegotiationMethodBase.php
index 9ed0f7c..272ddee 100644
--- a/core/modules/language/lib/Drupal/language/LanguageNegotiationMethodBase.php
+++ b/core/modules/language/lib/Drupal/language/LanguageNegotiationMethodBase.php
@@ -63,7 +63,7 @@ public function setCurrentUser(AccountInterface $current_user) {
    */
   public function persist(Language $language) {
     // Remember the method ID used to detect the language.
-    $language->method_id = static::METHOD_ID;
+    $language->setNegotiationMethodId(static::METHOD_ID);
   }
 
 }
diff --git a/core/modules/language/lib/Drupal/language/LanguageNegotiator.php b/core/modules/language/lib/Drupal/language/LanguageNegotiator.php
index 7841bab..298cf88 100644
--- a/core/modules/language/lib/Drupal/language/LanguageNegotiator.php
+++ b/core/modules/language/lib/Drupal/language/LanguageNegotiator.php
@@ -159,7 +159,7 @@ public function initializeType($type) {
     if (!$language) {
       // If no other language was found use the default one.
       $language = $this->languageManager->getDefaultLanguage();
-      $language->method_id = LanguageNegotiatorInterface::METHOD_ID;
+      $language->setNegotiationMethodId(LanguageNegotiatorInterface::METHOD_ID);
     }
 
     return $language;
diff --git a/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationSession.php b/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationSession.php
index e56278d..d0c8f82 100644
--- a/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationSession.php
+++ b/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationSession.php
@@ -127,7 +127,7 @@ function getLanguageSwitchLinks(Request $request, $type, $path) {
     $links = array();
     $config = $this->config->get('language.negotiation')->get('session');
     $param = $config['parameter'];
-    $language_query = isset($_SESSION[$param]) ? $_SESSION[$param] : $this->languageManager->getCurrentLanguage($type)->id;
+    $language_query = isset($_SESSION[$param]) ? $_SESSION[$param] : $this->languageManager->getCurrentLanguage($type)->getId();
     $query = array();
     parse_str($request->getQueryString(), $query);
 
diff --git a/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationUI.php b/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationUI.php
index 3b64974..92d3b01 100644
--- a/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationUI.php
+++ b/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationUI.php
@@ -32,7 +32,7 @@ class LanguageNegotiationUI extends LanguageNegotiationMethodBase {
    * {@inheritdoc}
    */
   public function getLangcode(Request $request = NULL) {
-    return $this->languageManager ? $this->languageManager->getCurrentLanguage()->id : NULL;
+    return $this->languageManager ? $this->languageManager->getCurrentLanguage()->getId() : NULL;
   }
 
 }
diff --git a/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationUrl.php b/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationUrl.php
index eacb5c4..b1e266d 100644
--- a/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationUrl.php
+++ b/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationUrl.php
@@ -138,12 +138,12 @@ public function processOutbound($path, &$options = array(), Request $request = N
     }
     $config = $this->config->get('language.negotiation')->get('url');
     if ($config['source'] == LanguageNegotiationUrl::CONFIG_PATH_PREFIX) {
-      if (is_object($options['language']) && !empty($config['prefixes'][$options['language']->id])) {
-        return empty($path) ? $config['prefixes'][$options['language']->id] : $config['prefixes'][$options['language']->id] . '/' . $path;
+      if (is_object($options['language']) && !empty($config['prefixes'][$options['language']->getId()])) {
+        return empty($path) ? $config['prefixes'][$options['language']->getId()] : $config['prefixes'][$options['language']->getId()] . '/' . $path;
       }
     }
     elseif ($config['source'] ==  LanguageNegotiationUrl::CONFIG_DOMAIN) {
-      if (is_object($options['language']) && !empty($config['domains'][$options['language']->id])) {
+      if (is_object($options['language']) && !empty($config['domains'][$options['language']->getId()])) {
 
         // Save the original base URL. If it contains a port, we need to
         // retain it below.
@@ -154,7 +154,7 @@ public function processOutbound($path, &$options = array(), Request $request = N
 
         // Ask for an absolute URL with our modified base URL.
         $options['absolute'] = TRUE;
-        $options['base_url'] = $url_scheme . '://' . $config['domains'][$options['language']->id];
+        $options['base_url'] = $url_scheme . '://' . $config['domains'][$options['language']->getId()];
 
         // In case either the original base URL or the HTTP host contains a
         // port, retain it.
diff --git a/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationUrlFallback.php b/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationUrlFallback.php
index 2310153..7c4fddf 100644
--- a/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationUrlFallback.php
+++ b/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationUrlFallback.php
@@ -62,11 +62,11 @@ public function getLangcode(Request $request = NULL) {
       // information, a missing URL language information indicates that URL
       // language should be the default one, otherwise we fall back to an
       // already detected language.
-      if (($prefix && empty($config['prefixes'][$default->id])) || (!$prefix && empty($config['domains'][$default->id]))) {
-        $langcode = $default->id;
+      if (($prefix && empty($config['prefixes'][$default->getId()])) || (!$prefix && empty($config['domains'][$default->getId()]))) {
+        $langcode = $default->getId();
       }
       else {
-        $langcode = $this->languageManager->getCurrentLanguage()->id;
+        $langcode = $this->languageManager->getCurrentLanguage()->getId();
       }
     }
 
diff --git a/core/modules/language/lib/Drupal/language/Tests/LanguageConfigurationElementTest.php b/core/modules/language/lib/Drupal/language/Tests/LanguageConfigurationElementTest.php
index 0a507f2..ee918b4 100644
--- a/core/modules/language/lib/Drupal/language/Tests/LanguageConfigurationElementTest.php
+++ b/core/modules/language/lib/Drupal/language/Tests/LanguageConfigurationElementTest.php
@@ -84,14 +84,14 @@ public function testDefaultLangcode() {
     language_save_default_configuration('custom_type', 'custom_bundle', array('langcode' => 'current_interface', 'language_show' => TRUE));
     $langcode = language_get_default_langcode('custom_type', 'custom_bundle');
     $language_interface = \Drupal::languageManager()->getCurrentLanguage();
-    $this->assertEqual($langcode, $language_interface->id);
+    $this->assertEqual($langcode, $language_interface->getId());
 
     // Site's default.
     $old_default = \Drupal::languageManager()->getDefaultLanguage();
-    $old_default->default = FALSE;
+    $old_default->setDefault(FALSE);
     language_save($old_default);
     $new_default = \Drupal::languageManager()->getLanguage('cc');
-    $new_default->default = TRUE;
+    $new_default->setDefault(TRUE);
     language_save($new_default);
     language_save_default_configuration('custom_type', 'custom_bundle', array('langcode' => 'site_default', 'language_show' => TRUE));
     $langcode = language_get_default_langcode('custom_type', 'custom_bundle');
diff --git a/core/modules/language/lib/Drupal/language/Tests/LanguageDependencyInjectionTest.php b/core/modules/language/lib/Drupal/language/Tests/LanguageDependencyInjectionTest.php
index 067c477..e2109b2 100644
--- a/core/modules/language/lib/Drupal/language/Tests/LanguageDependencyInjectionTest.php
+++ b/core/modules/language/lib/Drupal/language/Tests/LanguageDependencyInjectionTest.php
@@ -62,7 +62,7 @@ function testDependencyInjectedNewDefaultLanguage() {
     // The language system creates a Language object which contains the
     // same properties as the new default language object.
     $result = \Drupal::languageManager()->getCurrentLanguage();
-    $this->assertIdentical($result->id, 'fr');
+    $this->assertIdentical($result->getId(), 'fr');
 
     // Delete the language to check that we fallback to the default.
     try {
@@ -77,7 +77,7 @@ function testDependencyInjectedNewDefaultLanguage() {
     language_save($default_language);
     language_delete('fr');
     $result = \Drupal::languageManager()->getCurrentLanguage();
-    $this->assertIdentical($result->id, $default_language->id);
+    $this->assertIdentical($result->getId(), $default_language->id);
   }
 
 }
diff --git a/core/modules/language/tests/language_test/language_test.module b/core/modules/language/tests/language_test/language_test.module
index e1fd47e..296d091 100644
--- a/core/modules/language/tests/language_test/language_test.module
+++ b/core/modules/language/tests/language_test/language_test.module
@@ -13,8 +13,8 @@
  */
 function language_test_page_build() {
   language_test_store_language_negotiation();
-  if (isset(\Drupal::languageManager()->getCurrentLanguage()->id) && isset(\Drupal::languageManager()->getCurrentLanguage()->method_id)) {
-    drupal_set_message(t('Language negotiation method: @name', array('@name' => \Drupal::languageManager()->getCurrentLanguage()->method_id)));
+  if (\Drupal::languageManager()->getCurrentLanguage()->getId() && \Drupal::languageManager()->getCurrentLanguage()->getNegotiationMethodId()) {
+    drupal_set_message(t('Language negotiation method: @name', array('@name' => \Drupal::languageManager()->getCurrentLanguage()->getNegotiationMethodId())));
   }
 }
 
@@ -69,7 +69,7 @@ function language_test_store_language_negotiation() {
   if (\Drupal::moduleHandler()->moduleExists('language')) {
     $last = array();
     foreach (\Drupal::languageManager()->getDefinedLanguageTypes() as $type) {
-      $last[$type] = \Drupal::languageManager()->getCurrentLanguage($type)->id;
+      $last[$type] = \Drupal::languageManager()->getCurrentLanguage($type)->getId();
     }
     \Drupal::state()->set('language_test.language_negotiation_last', $last);
   }
diff --git a/core/modules/locale/lib/Drupal/locale/Form/TranslateFormBase.php b/core/modules/locale/lib/Drupal/locale/Form/TranslateFormBase.php
index c5447e0..efd59a5 100644
--- a/core/modules/locale/lib/Drupal/locale/Form/TranslateFormBase.php
+++ b/core/modules/locale/lib/Drupal/locale/Form/TranslateFormBase.php
@@ -171,7 +171,7 @@ protected function translateFilters() {
     }
 
     // Pick the current interface language code for the filter.
-    $default_langcode = $this->languageManager->getCurrentLanguage()->id;
+    $default_langcode = $this->languageManager->getCurrentLanguage()->getId();
     if (!isset($language_options[$default_langcode])) {
       $available_langcodes = array_keys($language_options);
       $default_langcode = array_shift($available_langcodes);
diff --git a/core/modules/locale/locale.module b/core/modules/locale/locale.module
index 881ca9a..984f491 100644
--- a/core/modules/locale/locale.module
+++ b/core/modules/locale/locale.module
@@ -301,7 +301,7 @@ function locale_get_plural($count, $langcode = NULL) {
   // individually for each language.
   $plural_indexes = &drupal_static(__FUNCTION__ . ':plurals', array());
 
-  $langcode = $langcode ? $langcode : $language_interface->id;
+  $langcode = $langcode ? $langcode : $language_interface->getId();
 
   if (!isset($plural_indexes[$langcode][$count])) {
     // Retrieve and statically cache the plural formulas for all languages.
@@ -588,11 +588,11 @@ function locale_js_translate(array $files = array()) {
   }
 
   // If necessary, rebuild the translation file for the current language.
-  if (!empty($parsed['refresh:' . $language_interface->id])) {
+  if (!empty($parsed['refresh:' . $language_interface->getId()])) {
     // Don't clear the refresh flag on failure, so that another try will
     // be performed later.
     if (_locale_rebuild_js()) {
-      unset($parsed['refresh:' . $language_interface->id]);
+      unset($parsed['refresh:' . $language_interface->getId()]);
     }
     // Store any changes after refresh was attempted.
     \Drupal::state()->set('system.javascript_parsed', $parsed);
@@ -606,9 +606,9 @@ function locale_js_translate(array $files = array()) {
   // Add the translation JavaScript file to the page.
   $locale_javascripts = \Drupal::state()->get('locale.translation.javascript') ?: array();
   $translation_file = NULL;
-  if (!empty($files) && !empty($locale_javascripts[$language_interface->id])) {
+  if (!empty($files) && !empty($locale_javascripts[$language_interface->getId()])) {
     // Add the translation JavaScript file to the page.
-    $translation_file = $dir . '/' . $language_interface->id . '_' . $locale_javascripts[$language_interface->id] . '.js';
+    $translation_file = $dir . '/' . $language_interface->getId() . '_' . $locale_javascripts[$language_interface->getId()] . '.js';
   }
   return $translation_file;
 }
@@ -626,7 +626,7 @@ function locale_library_alter(array &$library, $name) {
 
     $language_interface = \Drupal::languageManager()->getCurrentLanguage();
     $settings['jquery']['ui']['datepicker'] = array(
-      'isRTL' => $language_interface->direction == Language::DIRECTION_RTL,
+      'isRTL' => $language_interface->getDirection() == Language::DIRECTION_RTL,
       'firstDay' => \Drupal::config('system.date')->get('first_day'),
     );
     $library['js'][] = array(
@@ -799,20 +799,22 @@ function locale_system_file_system_settings_submit(&$form, $form_state) {
  * Implements hook_preprocess_HOOK() for node templates.
  */
 function locale_preprocess_node(&$variables) {
-  if ($variables['node']->language()->id != Language::LANGCODE_NOT_SPECIFIED) {
+  /** @var \Drupal\node\NodeInterface $node */
+  $node = $variables['node'];
+  if ($node->language()->getId() != Language::LANGCODE_NOT_SPECIFIED) {
     $language_interface = \Drupal::languageManager()->getCurrentLanguage();
 
-    $node_language = $variables['node']->language();
-    if ($node_language->id != $language_interface->id) {
+    $node_language = $node->language();
+    if ($node_language->getId() != $language_interface->getId()) {
       // If the node language was different from the page language, we should
       // add markup to identify the language. Otherwise the page language is
       // inherited.
-      $variables['attributes']['lang'] = $node_language->id;
-      if ($node_language->direction != $language_interface->direction) {
+      $variables['attributes']['lang'] = $node_language->getId();
+      if ($node_language->getDirection() != $language_interface->getDirection()) {
         // If text direction is different form the page's text direction, add
         // direction information as well.
         $dir = array('ltr', 'rtl');
-        $variables['attributes']['dir'] = $dir[$node_language->direction];
+        $variables['attributes']['dir'] = $dir[$node_language->getDirection()];
       }
     }
   }
@@ -1264,7 +1266,7 @@ function _locale_rebuild_js($langcode = NULL) {
   // Only add strings with a translation to the translations array.
   $conditions = array(
     'type' => 'javascript',
-    'language' =>  $language->id,
+    'language' =>  $language->getId(),
     'translated' => TRUE,
   );
   $translations = array();
@@ -1281,8 +1283,8 @@ function _locale_rebuild_js($langcode = NULL) {
     );
 
     $locale_plurals = \Drupal::state()->get('locale.translation.plurals') ?: array();
-    if (!empty($locale_plurals[$language->id]['formula'])) {
-      $data['pluralFormula'] = $locale_plurals[$language->id]['formula'];
+    if (!empty($locale_plurals[$language->getId()]['formula'])) {
+      $data['pluralFormula'] = $locale_plurals[$language->getId()]['formula'];
     }
 
     $data = 'Drupal.locale = ' . Json::encode($data) . ';';
@@ -1295,23 +1297,23 @@ function _locale_rebuild_js($langcode = NULL) {
 
   // Delete old file, if we have no translations anymore, or a different file to be saved.
   $locale_javascripts = \Drupal::state()->get('locale.translation.javascript') ?: array();
-  $changed_hash = !isset($locale_javascripts[$language->id]) || ($locale_javascripts[$language->id] != $data_hash);
-  if (!empty($locale_javascripts[$language->id]) && (!$data || $changed_hash)) {
-    file_unmanaged_delete($dir . '/' . $language->id . '_' . $locale_javascripts[$language->id] . '.js');
-    $locale_javascripts[$language->id] = '';
+  $changed_hash = !isset($locale_javascripts[$language->getId()]) || ($locale_javascripts[$language->getId()] != $data_hash);
+  if (!empty($locale_javascripts[$language->getId()]) && (!$data || $changed_hash)) {
+    file_unmanaged_delete($dir . '/' . $language->getId() . '_' . $locale_javascripts[$language->getId()] . '.js');
+    $locale_javascripts[$language->getId()] = '';
     $status = 'deleted';
   }
 
   // Only create a new file if the content has changed or the original file got
   // lost.
-  $dest = $dir . '/' . $language->id . '_' . $data_hash . '.js';
+  $dest = $dir . '/' . $language->getId() . '_' . $data_hash . '.js';
   if ($data && ($changed_hash || !file_exists($dest))) {
     // Ensure that the directory exists and is writable, if possible.
     file_prepare_directory($dir, FILE_CREATE_DIRECTORY);
 
     // Save the file.
     if (file_unmanaged_save_data($data, $dest)) {
-      $locale_javascripts[$language->id] = $data_hash;
+      $locale_javascripts[$language->getId()] = $data_hash;
       // If we deleted a previous version of the file and we replace it with a
       // new one we have an update.
       if ($status == 'deleted') {
@@ -1329,7 +1331,7 @@ function _locale_rebuild_js($langcode = NULL) {
       }
     }
     else {
-      $locale_javascripts[$language->id] = '';
+      $locale_javascripts[$language->getId()] = '';
       $status = 'error';
     }
   }
@@ -1344,21 +1346,21 @@ function _locale_rebuild_js($langcode = NULL) {
   // Log the operation and return success flag.
   switch ($status) {
     case 'updated':
-      watchdog('locale', 'Updated JavaScript translation file for the language %language.', array('%language' => $language->name));
+      watchdog('locale', 'Updated JavaScript translation file for the language %language.', array('%language' => $language->getName()));
       return TRUE;
 
     case 'rebuilt':
-      watchdog('locale', 'JavaScript translation file %file.js was lost.', array('%file' => $locale_javascripts[$language->id]), WATCHDOG_WARNING);
+      watchdog('locale', 'JavaScript translation file %file.js was lost.', array('%file' => $locale_javascripts[$language->getId()]), WATCHDOG_WARNING);
     // Proceed to the 'created' case as the JavaScript translation file has
     // been created again.
     case 'created':
-      watchdog('locale', 'Created JavaScript translation file for the language %language.', array('%language' => $language->name));
+      watchdog('locale', 'Created JavaScript translation file for the language %language.', array('%language' => $language->getName()));
       return TRUE;
     case 'deleted':
-      watchdog('locale', 'Removed JavaScript translation file for the language %language because no translations currently exist for that language.', array('%language' => $language->name));
+      watchdog('locale', 'Removed JavaScript translation file for the language %language because no translations currently exist for that language.', array('%language' => $language->getName()));
       return TRUE;
     case 'error':
-      watchdog('locale', 'An error occurred during creation of the JavaScript translation file for the language %language.', array('%language' => $language->name), WATCHDOG_ERROR);
+      watchdog('locale', 'An error occurred during creation of the JavaScript translation file for the language %language.', array('%language' => $language->getName()), WATCHDOG_ERROR);
       return FALSE;
     default:
       // No operation needed.
diff --git a/core/modules/menu_link/lib/Drupal/menu_link/MenuTree.php b/core/modules/menu_link/lib/Drupal/menu_link/MenuTree.php
index 24a531f..ea2f440 100644
--- a/core/modules/menu_link/lib/Drupal/menu_link/MenuTree.php
+++ b/core/modules/menu_link/lib/Drupal/menu_link/MenuTree.php
@@ -155,7 +155,7 @@ public function buildAllData($menu_name, $link = NULL, $max_depth = NULL) {
     $mlid = isset($link['mlid']) ? $link['mlid'] : 0;
     // Generate a cache ID (cid) specific for this $menu_name, $link, $language,
     // and depth.
-    $cid = 'links:' . $menu_name . ':all:' . $mlid . ':' . $language_interface->id . ':' . (int) $max_depth;
+    $cid = 'links:' . $menu_name . ':all:' . $mlid . ':' . $language_interface->getId() . ':' . (int) $max_depth;
 
     if (!isset($this->menuFullTrees[$cid])) {
       // If the static variable doesn't have the data, check {cache_menu}.
@@ -218,7 +218,7 @@ public function buildPageData($menu_name, $max_depth = NULL, $only_active_trail
         $max_depth = min($max_depth, MENU_MAX_DEPTH);
       }
       // Generate a cache ID (cid) specific for this page.
-      $cid = 'links:' . $menu_name . ':page:' . $system_path . ':' . $language_interface->id . ':' . $page_not_403 . ':' . (int) $max_depth;
+      $cid = 'links:' . $menu_name . ':page:' . $system_path . ':' . $language_interface->getId() . ':' . $page_not_403 . ':' . (int) $max_depth;
       // If we are asked for the active trail only, and $menu_name has not been
       // built and cached for this page yet, then this likely means that it
       // won't be built anymore, as this function is invoked from
@@ -455,7 +455,7 @@ protected function doBuildTree($menu_name, array $parameters = array()) {
     if (isset($parameters['expanded'])) {
       sort($parameters['expanded']);
     }
-    $tree_cid = 'links:' . $menu_name . ':tree-data:' . $language_interface->id . ':' . hash('sha256', serialize($parameters));
+    $tree_cid = 'links:' . $menu_name . ':tree-data:' . $language_interface->getId() . ':' . hash('sha256', serialize($parameters));
 
     // If we do not have this tree in the static cache, check {cache_menu}.
     if (!isset($this->menuTree[$tree_cid])) {
diff --git a/core/modules/node/lib/Drupal/node/Controller/NodeController.php b/core/modules/node/lib/Drupal/node/Controller/NodeController.php
index b16b93d..9939437 100644
--- a/core/modules/node/lib/Drupal/node/Controller/NodeController.php
+++ b/core/modules/node/lib/Drupal/node/Controller/NodeController.php
@@ -69,7 +69,7 @@ public function add(NodeTypeInterface $node_type) {
       'uid' => $account->id(),
       'name' => $account->getUsername() ?: '',
       'type' => $node_type->type,
-      'langcode' => $langcode ? $langcode : $this->languageManager()->getCurrentLanguage()->id,
+      'langcode' => $langcode ? $langcode : $this->languageManager()->getCurrentLanguage()->getId(),
     ));
 
     $form = $this->entityFormBuilder()->getForm($node);
diff --git a/core/modules/node/lib/Drupal/node/Entity/Node.php b/core/modules/node/lib/Drupal/node/Entity/Node.php
index d5aea78..e9790ae 100644
--- a/core/modules/node/lib/Drupal/node/Entity/Node.php
+++ b/core/modules/node/lib/Drupal/node/Entity/Node.php
@@ -176,7 +176,7 @@ public function prepareLangcode() {
       // Load languages the node exists in.
       $node_translations = $this->getTranslationLanguages();
       // Load the language from content negotiation.
-      $content_negotiation_langcode = \Drupal::languageManager()->getCurrentLanguage(Language::TYPE_CONTENT)->id;
+      $content_negotiation_langcode = \Drupal::languageManager()->getCurrentLanguage(Language::TYPE_CONTENT)->getId();
       // If there is a translation available, use it.
       if (isset($node_translations[$content_negotiation_langcode])) {
         $langcode = $content_negotiation_langcode;
diff --git a/core/modules/node/node.module b/core/modules/node/node.module
index d793975..d9d9437 100644
--- a/core/modules/node/node.module
+++ b/core/modules/node/node.module
@@ -318,7 +318,7 @@ function node_type_get_types() {
  *   An array of node type labels, keyed by the node type name.
  */
 function node_type_get_names() {
-  $cid = 'node_type:names:' . \Drupal::languageManager()->getCurrentLanguage()->id;
+  $cid = 'node_type:names:' . \Drupal::languageManager()->getCurrentLanguage()->getId();
   if ($cache = \Drupal::cache()->get($cid)) {
     return $cache->data;
   }
@@ -1173,7 +1173,7 @@ function node_feed($nids = FALSE, $channel = array()) {
     'title'       => \Drupal::config('system.site')->get('name'),
     'link'        => $base_url,
     'description' => $rss_config->get('channel.description'),
-    'language'    => $language_content->id
+    'language'    => $language_content->getId()
   );
   $channel_extras = array_diff_key($channel, $channel_defaults);
   $channel = array_merge($channel_defaults, $channel);
diff --git a/core/modules/search/search.pages.inc b/core/modules/search/search.pages.inc
index 34b235c..1dc7ed0 100644
--- a/core/modules/search/search.pages.inc
+++ b/core/modules/search/search.pages.inc
@@ -36,7 +36,7 @@ function template_preprocess_search_result(&$variables) {
   $result = $variables['result'];
   $variables['url'] = check_url($result['link']);
   $variables['title'] = check_plain($result['title']);
-  if (isset($result['language']) && $result['language'] != $language_interface->id && $result['language'] != Language::LANGCODE_NOT_SPECIFIED) {
+  if (isset($result['language']) && $result['language'] != $language_interface->getId() && $result['language'] != Language::LANGCODE_NOT_SPECIFIED) {
     $variables['title_attributes']['lang'] = $result['language'];
     $variables['content_attributes']['lang'] = $result['language'];
   }
diff --git a/core/modules/statistics/lib/Drupal/statistics/Tests/StatisticsTokenReplaceTest.php b/core/modules/statistics/lib/Drupal/statistics/Tests/StatisticsTokenReplaceTest.php
index 712c5ab..115b1c9 100644
--- a/core/modules/statistics/lib/Drupal/statistics/Tests/StatisticsTokenReplaceTest.php
+++ b/core/modules/statistics/lib/Drupal/statistics/Tests/StatisticsTokenReplaceTest.php
@@ -56,7 +56,7 @@ function testStatisticsTokenReplacement() {
     $this->assertFalse(in_array(0, array_map('strlen', $tests)), 'No empty tokens generated.');
 
     foreach ($tests as $input => $expected) {
-      $output = \Drupal::token()->replace($input, array('node' => $node), array('langcode' => $language_interface->id));
+      $output = \Drupal::token()->replace($input, array('node' => $node), array('langcode' => $language_interface->getId()));
       $this->assertEqual($output, $expected, format_string('Statistics token %token replaced.', array('%token' => $input)));
     }
   }
diff --git a/core/modules/system/core.api.php b/core/modules/system/core.api.php
index 5ff42fe..cd92418 100644
--- a/core/modules/system/core.api.php
+++ b/core/modules/system/core.api.php
@@ -201,7 +201,7 @@
  *
  * Example:
  * @code
- * $cid = 'mymodule_example:' . \Drupal::languageManager()->getCurrentLanguage()->id();
+ * $cid = 'mymodule_example:' . \Drupal::languageManager()->getCurrentLanguage()->getId();
  *
  * $data = NULL;
  * if ($cache = \Drupal::cache()->get($cid)) {
diff --git a/core/modules/system/language.api.php b/core/modules/system/language.api.php
index ed6de6c..7ed7fce 100644
--- a/core/modules/system/language.api.php
+++ b/core/modules/system/language.api.php
@@ -28,7 +28,7 @@ function hook_language_switch_links_alter(array &$links, $type, $path) {
   $language_interface = \Drupal::languageManager()->getCurrentLanguage();
 
   if ($type == \Drupal\Core\Language\Language::TYPE_CONTENT && isset($links[$language_interface->id])) {
-    foreach ($links[$language_interface->id] as $link) {
+    foreach ($links[$language_interface->getId()] as $link) {
       $link['attributes']['class'][] = 'active-language';
     }
   }
diff --git a/core/modules/system/lib/Drupal/system/Tests/Common/FormatDateTest.php b/core/modules/system/lib/Drupal/system/Tests/Common/FormatDateTest.php
index 1a6b758..aa085bf 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Common/FormatDateTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Common/FormatDateTest.php
@@ -132,8 +132,8 @@ function testFormatDate() {
     // Save the original user and language and then replace it with the test user and language.
     $real_user = $user;
     $user = user_load($test_user->id(), TRUE);
-    $real_language = $language_interface->id;
-    $language_interface->id = $user->getPreferredLangcode();
+    $real_language = $language_interface->getId();
+    $language_interface->setId($user->getPreferredLangcode());
     // Simulate a Drupal bootstrap with the logged-in user.
     date_default_timezone_set(drupal_get_user_timezone());
 
@@ -155,7 +155,7 @@ function testFormatDate() {
 
     // Restore the original user and language, and enable session saving.
     $user = $real_user;
-    $language_interface->id = $real_language;
+    $language_interface->setId($real_language);
     // Restore default time zone.
     date_default_timezone_set(drupal_get_user_timezone());
     drupal_save_session(TRUE);
diff --git a/core/modules/system/lib/Drupal/system/Tests/Common/RenderElementTypesTest.php b/core/modules/system/lib/Drupal/system/Tests/Common/RenderElementTypesTest.php
index 001b807..c6196bf 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Common/RenderElementTypesTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Common/RenderElementTypesTest.php
@@ -156,9 +156,9 @@ function testMaintenancePage() {
 
     // HTML element attributes.
     $html_attributes = new Attribute;
-    $language_interface = \Drupal::service('language_manager')->getCurrentLanguage();
-    $html_attributes['lang'] = $language_interface->id;
-    $html_attributes['dir'] = $language_interface->direction ? 'rtl' : 'ltr';
+    $language_interface = \Drupal::languageManager()->getCurrentLanguage();
+    $html_attributes['lang'] = $language_interface->getId();
+    $html_attributes['dir'] = $language_interface->getDirection() ? 'rtl' : 'ltr';
 
     $site_config = \Drupal::config('system.site');
 
diff --git a/core/modules/system/lib/Drupal/system/Tests/Entity/EntityTranslationTest.php b/core/modules/system/lib/Drupal/system/Tests/Entity/EntityTranslationTest.php
index 58ad4c3..e6c8aa4 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Entity/EntityTranslationTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Entity/EntityTranslationTest.php
@@ -448,7 +448,7 @@ function testEntityTranslationAPI() {
    * Tests language fallback applied to field and entity translations.
    */
   function testLanguageFallback() {
-    $current_langcode = $this->languageManager->getCurrentLanguage(Language::TYPE_CONTENT)->id;
+    $current_langcode = $this->languageManager->getCurrentLanguage(Language::TYPE_CONTENT)->getId();
     $this->langcodes[] = $current_langcode;
 
     $values = array();
diff --git a/core/modules/system/lib/Drupal/system/Tests/Mail/MailTest.php b/core/modules/system/lib/Drupal/system/Tests/Mail/MailTest.php
index 56aef7f..27d0d87 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Mail/MailTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Mail/MailTest.php
@@ -67,7 +67,7 @@ public function testCancelMessage() {
     \Drupal::state()->set('system.test_mail_collector', array());
 
     // Send a test message that simpletest_mail_alter should cancel.
-    drupal_mail('simpletest', 'cancel_test', 'cancel@example.com', $language_interface->id);
+    drupal_mail('simpletest', 'cancel_test', 'cancel@example.com', $language_interface->getId());
     // Retrieve sent message.
     $captured_emails = \Drupal::state()->get('system.test_mail_collector');
     $sent_message = end($captured_emails);
diff --git a/core/modules/system/system.api.php b/core/modules/system/system.api.php
index b995551..1f5eb6e 100644
--- a/core/modules/system/system.api.php
+++ b/core/modules/system/system.api.php
@@ -327,7 +327,7 @@ function hook_library_alter(array &$library, $name) {
 
     $language_interface = \Drupal::languageManager()->getCurrentLanguage();
     $settings['jquery']['ui']['datepicker'] = array(
-      'isRTL' => $language_interface->direction == Language::DIRECTION_RTL,
+      'isRTL' => $language_interface->getDirection() == Language::DIRECTION_RTL,
       'firstDay' => \Drupal::config('system.date')->get('first_day'),
     );
     $library['js'][] = array(
@@ -1285,7 +1285,7 @@ function hook_watchdog(array $log_entry) {
     '@message'       => strip_tags($log_entry['message']),
   ));
 
-  drupal_mail('emaillog', 'entry', $to, $language_interface->id, $params);
+  drupal_mail('emaillog', 'entry', $to, $language_interface->getId(), $params);
 }
 
 /**
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index ad8c084..b125268 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -967,7 +967,7 @@ function system_page_build(&$page) {
       array(
         'path' => current_path(),
         'front' => drupal_is_front_page(),
-        'language' => \Drupal::languageManager()->getCurrentLanguage(\Drupal\Core\Language\Language::TYPE_URL)->id,
+        'language' => \Drupal::languageManager()->getCurrentLanguage(\Drupal\Core\Language\Language::TYPE_URL)->getId(),
         'query' => \Drupal::service('request')->query->all(),
       )
     );
diff --git a/core/modules/system/tests/modules/plugin_test/lib/Drupal/plugin_test/Plugin/CachedMockBlockManager.php b/core/modules/system/tests/modules/plugin_test/lib/Drupal/plugin_test/Plugin/CachedMockBlockManager.php
index df79b31..61ad702 100644
--- a/core/modules/system/tests/modules/plugin_test/lib/Drupal/plugin_test/Plugin/CachedMockBlockManager.php
+++ b/core/modules/system/tests/modules/plugin_test/lib/Drupal/plugin_test/Plugin/CachedMockBlockManager.php
@@ -25,6 +25,6 @@ public function __construct() {
     // The CacheDecorator allows us to cache these plugin definitions for
     // quicker retrieval. In this case we are generating a cache key by
     // language.
-    $this->discovery = new CacheDecorator($this->discovery, 'mock_block:' . \Drupal::languageManager()->getCurrentLanguage()->id, 'default',  1542646800, array('plugin_test'));
+    $this->discovery = new CacheDecorator($this->discovery, 'mock_block:' . \Drupal::languageManager()->getCurrentLanguage()->getId(), 'default',  1542646800, array('plugin_test'));
   }
 }
diff --git a/core/modules/system/theme.api.php b/core/modules/system/theme.api.php
index 50fa74e..8d121f6 100644
--- a/core/modules/system/theme.api.php
+++ b/core/modules/system/theme.api.php
@@ -288,7 +288,7 @@ function hook_theme_suggestions_HOOK(array $variables) {
  */
 function hook_theme_suggestions_alter(array &$suggestions, array $variables, $hook) {
   // Add an interface-language specific suggestion to all theme hooks.
-  $suggestions[] = $hook . '__' . \Drupal::languageManager()->getCurrentLanguage()->id;
+  $suggestions[] = $hook . '__' . \Drupal::languageManager()->getCurrentLanguage()->getId();
 }
 
 /**
diff --git a/core/modules/taxonomy/lib/Drupal/taxonomy/Tests/TokenReplaceTest.php b/core/modules/taxonomy/lib/Drupal/taxonomy/Tests/TokenReplaceTest.php
index a09cbc2..806f43a 100644
--- a/core/modules/taxonomy/lib/Drupal/taxonomy/Tests/TokenReplaceTest.php
+++ b/core/modules/taxonomy/lib/Drupal/taxonomy/Tests/TokenReplaceTest.php
@@ -97,7 +97,7 @@ function testTaxonomyTokenReplacement() {
     $tests['[term:vocabulary:name]'] = String::checkPlain($this->vocabulary->name);
 
     foreach ($tests as $input => $expected) {
-      $output = $token_service->replace($input, array('term' => $term1), array('langcode' => $language_interface->id));
+      $output = $token_service->replace($input, array('term' => $term1), array('langcode' => $language_interface->getId()));
       $this->assertEqual($output, $expected, format_string('Sanitized taxonomy term token %token replaced.', array('%token' => $input)));
     }
 
@@ -117,7 +117,7 @@ function testTaxonomyTokenReplacement() {
     $this->assertFalse(in_array(0, array_map('strlen', $tests)), 'No empty tokens generated.');
 
     foreach ($tests as $input => $expected) {
-      $output = $token_service->replace($input, array('term' => $term2), array('langcode' => $language_interface->id));
+      $output = $token_service->replace($input, array('term' => $term2), array('langcode' => $language_interface->getId()));
       $this->assertEqual($output, $expected, format_string('Sanitized taxonomy term token %token replaced.', array('%token' => $input)));
     }
 
@@ -128,7 +128,7 @@ function testTaxonomyTokenReplacement() {
     $tests['[term:vocabulary:name]'] = $this->vocabulary->name;
 
     foreach ($tests as $input => $expected) {
-      $output = $token_service->replace($input, array('term' => $term2), array('langcode' => $language_interface->id, 'sanitize' => FALSE));
+      $output = $token_service->replace($input, array('term' => $term2), array('langcode' => $language_interface->getId(), 'sanitize' => FALSE));
       $this->assertEqual($output, $expected, format_string('Unsanitized taxonomy term token %token replaced.', array('%token' => $input)));
     }
 
@@ -144,7 +144,7 @@ function testTaxonomyTokenReplacement() {
     $this->assertFalse(in_array(0, array_map('strlen', $tests)), 'No empty tokens generated.');
 
     foreach ($tests as $input => $expected) {
-      $output = $token_service->replace($input, array('vocabulary' => $this->vocabulary), array('langcode' => $language_interface->id));
+      $output = $token_service->replace($input, array('vocabulary' => $this->vocabulary), array('langcode' => $language_interface->getId()));
       $this->assertEqual($output, $expected, format_string('Sanitized taxonomy vocabulary token %token replaced.', array('%token' => $input)));
     }
 
@@ -153,7 +153,7 @@ function testTaxonomyTokenReplacement() {
     $tests['[vocabulary:description]'] = $this->vocabulary->description;
 
     foreach ($tests as $input => $expected) {
-      $output = $token_service->replace($input, array('vocabulary' => $this->vocabulary), array('langcode' => $language_interface->id, 'sanitize' => FALSE));
+      $output = $token_service->replace($input, array('vocabulary' => $this->vocabulary), array('langcode' => $language_interface->getId(), 'sanitize' => FALSE));
       $this->assertEqual($output, $expected, format_string('Unsanitized taxonomy vocabulary token %token replaced.', array('%token' => $input)));
     }
   }
diff --git a/core/modules/toolbar/toolbar.module b/core/modules/toolbar/toolbar.module
index 0f58cb2..776feed 100644
--- a/core/modules/toolbar/toolbar.module
+++ b/core/modules/toolbar/toolbar.module
@@ -378,7 +378,7 @@ function toolbar_toolbar() {
   // toolbar_subtrees route. We provide the JavaScript requesting that JSONP
   // script here with the hash parameter that is needed for that route.
   // @see toolbar_subtrees_jsonp()
-  $langcode = \Drupal::languageManager()->getCurrentLanguage()->id;
+  $langcode = \Drupal::languageManager()->getCurrentLanguage()->getId();
   $menu['toolbar_administration']['#attached']['js'][] = array(
     'type' => 'setting',
     'data' => array('toolbar' => array(
diff --git a/core/modules/user/lib/Drupal/user/AccountFormController.php b/core/modules/user/lib/Drupal/user/AccountFormController.php
index ed4cc07..11df204 100644
--- a/core/modules/user/lib/Drupal/user/AccountFormController.php
+++ b/core/modules/user/lib/Drupal/user/AccountFormController.php
@@ -233,9 +233,9 @@ public function form(array $form, array &$form_state) {
       );
     }
 
-    $user_preferred_langcode = $register ? $language_interface->id : $account->getPreferredLangcode();
+    $user_preferred_langcode = $register ? $language_interface->getId() : $account->getPreferredLangcode();
 
-    $user_preferred_admin_langcode = $register ? $language_interface->id : $account->getPreferredAdminLangcode();
+    $user_preferred_admin_langcode = $register ? $language_interface->getId() : $account->getPreferredAdminLangcode();
 
     // Is the user preferred language enabled?
     $user_language_enabled = FALSE;
diff --git a/core/modules/user/lib/Drupal/user/Form/UserPasswordForm.php b/core/modules/user/lib/Drupal/user/Form/UserPasswordForm.php
index 15d48c8..3ee7e6b 100644
--- a/core/modules/user/lib/Drupal/user/Form/UserPasswordForm.php
+++ b/core/modules/user/lib/Drupal/user/Form/UserPasswordForm.php
@@ -128,7 +128,7 @@ public function validateForm(array &$form, array &$form_state) {
    * {@inheritdoc}
    */
   public function submitForm(array &$form, array &$form_state) {
-    $langcode = $this->languageManager->getCurrentLanguage()->id;
+    $langcode = $this->languageManager->getCurrentLanguage()->getId();
 
     $account = $form_state['values']['account'];
     // Mail one time login URL and instructions using current language.
diff --git a/core/modules/user/lib/Drupal/user/Tests/UserTokenReplaceTest.php b/core/modules/user/lib/Drupal/user/Tests/UserTokenReplaceTest.php
index c9be29c..e87fbe1 100644
--- a/core/modules/user/lib/Drupal/user/Tests/UserTokenReplaceTest.php
+++ b/core/modules/user/lib/Drupal/user/Tests/UserTokenReplaceTest.php
@@ -66,17 +66,17 @@ function testUserTokenReplacement() {
     $tests['[user:mail]'] = check_plain($account->getEmail());
     $tests['[user:url]'] = url("user/" . $account->id(), $url_options);
     $tests['[user:edit-url]'] = url("user/" . $account->id() . "/edit", $url_options);
-    $tests['[user:last-login]'] = format_date($account->getLastLoginTime(), 'medium', '', NULL, $language_interface->id);
-    $tests['[user:last-login:short]'] = format_date($account->getLastLoginTime(), 'short', '', NULL, $language_interface->id);
-    $tests['[user:created]'] = format_date($account->getCreatedTime(), 'medium', '', NULL, $language_interface->id);
-    $tests['[user:created:short]'] = format_date($account->getCreatedTime(), 'short', '', NULL, $language_interface->id);
+    $tests['[user:last-login]'] = format_date($account->getLastLoginTime(), 'medium', '', NULL, $language_interface->getId());
+    $tests['[user:last-login:short]'] = format_date($account->getLastLoginTime(), 'short', '', NULL, $language_interface->getId());
+    $tests['[user:created]'] = format_date($account->getCreatedTime(), 'medium', '', NULL, $language_interface->getId());
+    $tests['[user:created:short]'] = format_date($account->getCreatedTime(), 'short', '', NULL, $language_interface->getId());
     $tests['[current-user:name]'] = check_plain(user_format_name($global_account));
 
     // Test to make sure that we generated something for each token.
     $this->assertFalse(in_array(0, array_map('strlen', $tests)), 'No empty tokens generated.');
 
     foreach ($tests as $input => $expected) {
-      $output = $token_service->replace($input, array('user' => $account), array('langcode' => $language_interface->id));
+      $output = $token_service->replace($input, array('user' => $account), array('langcode' => $language_interface->getId()));
       $this->assertEqual($output, $expected, format_string('Sanitized user token %token replaced.', array('%token' => $input)));
     }
 
@@ -86,7 +86,7 @@ function testUserTokenReplacement() {
     $tests['[current-user:name]'] = user_format_name($global_account);
 
     foreach ($tests as $input => $expected) {
-      $output = $token_service->replace($input, array('user' => $account), array('langcode' => $language_interface->id, 'sanitize' => FALSE));
+      $output = $token_service->replace($input, array('user' => $account), array('langcode' => $language_interface->getId(), 'sanitize' => FALSE));
       $this->assertEqual($output, $expected, format_string('Unsanitized user token %token replaced.', array('%token' => $input)));
     }
 
@@ -98,7 +98,7 @@ function testUserTokenReplacement() {
     // Generate tokens with interface language.
     $link = url('user', array('absolute' => TRUE));
     foreach ($tests as $input => $expected) {
-      $output = $token_service->replace($input, array('user' => $account), array('langcode' => $language_interface->id, 'callback' => 'user_mail_tokens', 'sanitize' => FALSE, 'clear' => TRUE));
+      $output = $token_service->replace($input, array('user' => $account), array('langcode' => $language_interface->getId(), 'callback' => 'user_mail_tokens', 'sanitize' => FALSE, 'clear' => TRUE));
       $this->assertTrue(strpos($output, $link) === 0, 'Generated URL is in interface language.');
     }
 
diff --git a/core/modules/views/lib/Drupal/views/Plugin/views/cache/CachePluginBase.php b/core/modules/views/lib/Drupal/views/Plugin/views/cache/CachePluginBase.php
index 9363e85..a438ed7 100644
--- a/core/modules/views/lib/Drupal/views/Plugin/views/cache/CachePluginBase.php
+++ b/core/modules/views/lib/Drupal/views/Plugin/views/cache/CachePluginBase.php
@@ -294,7 +294,7 @@ public function generateResultsKey() {
         'build_info' => $build_info,
         'roles' => $user->getRoles(),
         'super-user' => $user->id() == 1, // special caching for super user.
-        'langcode' => \Drupal::languageManager()->getCurrentLanguage()->id,
+        'langcode' => \Drupal::languageManager()->getCurrentLanguage()->getId(),
         'base_url' => $GLOBALS['base_url'],
       );
       $request = \Drupal::request();
@@ -324,7 +324,7 @@ public function generateOutputKey() {
         'roles' => $user->getRoles(),
         'super-user' => $user->id() == 1, // special caching for super user.
         'theme' => $GLOBALS['theme'],
-        'langcode' => \Drupal::languageManager()->getCurrentLanguage()->id,
+        'langcode' => \Drupal::languageManager()->getCurrentLanguage()->getId(),
         'base_url' => $GLOBALS['base_url'],
       );
 
diff --git a/core/modules/views/lib/Drupal/views/Plugin/views/display/DisplayPluginBase.php b/core/modules/views/lib/Drupal/views/Plugin/views/display/DisplayPluginBase.php
index d6fe40a..07db860 100644
--- a/core/modules/views/lib/Drupal/views/Plugin/views/display/DisplayPluginBase.php
+++ b/core/modules/views/lib/Drupal/views/Plugin/views/display/DisplayPluginBase.php
@@ -157,7 +157,7 @@ public function initDisplay(ViewExecutable $view, array &$display, array &$optio
     $skip_cache = \Drupal::config('views.settings')->get('skip_cache');
 
     if (empty($view->editing) || !$skip_cache) {
-      $cid = 'views:unpack_options:' . hash('sha256', serialize(array($this->options, $options))) . ':' . \Drupal::languageManager()->getCurrentLanguage()->id;
+      $cid = 'views:unpack_options:' . hash('sha256', serialize(array($this->options, $options))) . ':' . \Drupal::languageManager()->getCurrentLanguage()->getId();
       if (empty(static::$unpackOptions[$cid])) {
         $cache = \Drupal::cache('data')->get($cid);
         if (!empty($cache->data)) {
diff --git a/core/modules/views/lib/Drupal/views/ViewsData.php b/core/modules/views/lib/Drupal/views/ViewsData.php
index a1e2da4..2b17a8b 100644
--- a/core/modules/views/lib/Drupal/views/ViewsData.php
+++ b/core/modules/views/lib/Drupal/views/ViewsData.php
@@ -96,7 +96,7 @@ public function __construct(CacheBackendInterface $cache_backend, ConfigFactoryI
     $this->moduleHandler = $module_handler;
     $this->languageManager = $language_manager;
 
-    $this->langcode = $this->languageManager->getCurrentLanguage()->id;
+    $this->langcode = $this->languageManager->getCurrentLanguage()->getId();
     $this->skipCache = $config->get('views.settings')->get('skip_cache');
   }
 
diff --git a/core/modules/views/views.api.php b/core/modules/views/views.api.php
index f1551e2..06ef97d 100644
--- a/core/modules/views/views.api.php
+++ b/core/modules/views/views.api.php
@@ -341,8 +341,8 @@ function hook_views_query_substitutions(ViewExecutable $view) {
   return array(
     '***CURRENT_VERSION***' => \Drupal::VERSION,
     '***CURRENT_TIME***' => REQUEST_TIME,
-    '***CURRENT_LANGUAGE***' => \Drupal::languageManager()->getCurrentLanguage(\Drupal\Core\Language\Language::TYPE_CONTENT)->id,
-    '***DEFAULT_LANGUAGE***' => \Drupal::languageManager()->getDefaultLanguage()->id,
+    '***CURRENT_LANGUAGE***' => \Drupal::languageManager()->getCurrentLanguage(\Drupal\Core\Language\Language::TYPE_CONTENT)->getId(),
+    '***DEFAULT_LANGUAGE***' => \Drupal::languageManager()->getDefaultLanguage()->getId(),
   );
 }
 
diff --git a/core/modules/views/views.theme.inc b/core/modules/views/views.theme.inc
index d01235d..eae32ff 100644
--- a/core/modules/views/views.theme.inc
+++ b/core/modules/views/views.theme.inc
@@ -995,7 +995,7 @@ function template_preprocess_views_view_rss(&$variables) {
     $variables['link'] = check_url(url($path, $url_options));
   }
 
-  $variables['langcode'] = String::checkPlain(\Drupal::languageManager()->getCurrentLanguage()->id);
+  $variables['langcode'] = String::checkPlain(\Drupal::languageManager()->getCurrentLanguage()->getId());
   $variables['namespaces'] = new Attribute($style->namespaces);
   $variables['items'] = $items;
   $variables['channel_elements'] = format_xml_elements($style->channel_elements);
diff --git a/core/modules/views/views.views_execution.inc b/core/modules/views/views.views_execution.inc
index d1c040f..e6d4910 100644
--- a/core/modules/views/views.views_execution.inc
+++ b/core/modules/views/views.views_execution.inc
@@ -17,7 +17,7 @@ function views_views_query_substitutions(ViewExecutable $view) {
   return array(
     '***CURRENT_VERSION***' => \Drupal::VERSION,
     '***CURRENT_TIME***' => REQUEST_TIME,
-    '***CURRENT_LANGUAGE***' => \Drupal::languageManager()->getCurrentLanguage(Language::TYPE_CONTENT)->id,
-    '***DEFAULT_LANGUAGE***' => \Drupal::languageManager()->getDefaultLanguage()->id,
+    '***CURRENT_LANGUAGE***' => \Drupal::languageManager()->getCurrentLanguage(Language::TYPE_CONTENT)->getId(),
+    '***DEFAULT_LANGUAGE***' => \Drupal::languageManager()->getDefaultLanguage()->getId(),
   );
 }