diff --git a/core/modules/language/lib/Drupal/language/Plugin/views/field/LanguageField.php b/core/modules/language/lib/Drupal/language/Plugin/views/field/LanguageField.php
index 3909fcd..152104d 100644
--- a/core/modules/language/lib/Drupal/language/Plugin/views/field/LanguageField.php
+++ b/core/modules/language/lib/Drupal/language/Plugin/views/field/LanguageField.php
@@ -44,7 +44,7 @@ class LanguageField extends FieldPluginBase {
     // ready, see http://drupal.org/node/1616594.
     $value = $this->getValue($values);
     $language = language_load($value);
-    return $language ? $language->name : '';
+    return $language ? $language->getName() : '';
   }
 
 }
diff --git a/core/modules/node/lib/Drupal/node/Tests/NodeAccessLanguageTest.php b/core/modules/node/lib/Drupal/node/Tests/NodeAccessLanguageTest.php
index 2091878..e90b48b 100644
--- a/core/modules/node/lib/Drupal/node/Tests/NodeAccessLanguageTest.php
+++ b/core/modules/node/lib/Drupal/node/Tests/NodeAccessLanguageTest.php
@@ -8,6 +8,7 @@
 namespace Drupal\node\Tests;
 
 use Drupal\Core\Language\Language;
+use Drupal\Core\Language\LanguageInterface;
 
 /**
  * Verifies node access functionality for multiple languages.
diff --git a/core/modules/node/lib/Drupal/node/Tests/NodeTokenReplaceTest.php b/core/modules/node/lib/Drupal/node/Tests/NodeTokenReplaceTest.php
index 1f37118..dc959c1 100644
--- a/core/modules/node/lib/Drupal/node/Tests/NodeTokenReplaceTest.php
+++ b/core/modules/node/lib/Drupal/node/Tests/NodeTokenReplaceTest.php
@@ -82,8 +82,8 @@ function testNodeTokenReplacement() {
     $tests['[node:author]'] = String::checkPlain($account->getUsername());
     $tests['[node:author:uid]'] = $node->getOwnerId();
     $tests['[node:author:name]'] = String::checkPlain($account->getUsername());
-    $tests['[node:created:since]'] = \Drupal::service('date')->formatInterval(REQUEST_TIME - $node->getCreatedTime(), 2, $this->languageInterface->id);
-    $tests['[node:changed:since]'] = \Drupal::service('date')->formatInterval(REQUEST_TIME - $node->getChangedTime(), 2, $this->languageInterface->id);
+    $tests['[node:created:since]'] = \Drupal::service('date')->formatInterval(REQUEST_TIME - $node->getCreatedTime(), 2, $this->languageInterface->getId());
+    $tests['[node:changed:since]'] = \Drupal::service('date')->formatInterval(REQUEST_TIME - $node->getChangedTime(), 2, $this->languageInterface-getId());
 
     // Test to make sure that we generated something for each token.
     $this->assertFalse(in_array(0, array_map('strlen', $tests)), 'No empty tokens generated.');
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 37ce3f2..1e5a08a 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Entity/EntityTranslationTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Entity/EntityTranslationTest.php
@@ -476,7 +476,7 @@ function testLanguageFallback() {
 
     // Check that language fallback respects language weight by default.
     $languages = $this->languageManager->getLanguages();
-    $languages[$langcode]->weight = -1;
+    $languages[$langcode]->setWeight(-1);
     language_save($languages[$langcode]);
     $translation = $this->entityManager->getTranslationFromContext($entity, $langcode2);
     $this->assertEqual($translation->language()->getId(), $langcode, 'The current translation language matches the expected one.');
diff --git a/core/modules/system/lib/Drupal/system/Tests/System/TokenReplaceUnitTest.php b/core/modules/system/lib/Drupal/system/Tests/System/TokenReplaceUnitTest.php
index 623d995..fefc8d7 100644
--- a/core/modules/system/lib/Drupal/system/Tests/System/TokenReplaceUnitTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/System/TokenReplaceUnitTest.php
@@ -45,7 +45,7 @@ class TokenReplaceUnitTest extends TokenReplaceUnitTestBase {
     foreach ($tests as $test) {
       $input = $test['prefix'] . '[site:name]' . $test['suffix'];
       $expected = $test['prefix'] . 'Drupal' . $test['suffix'];
-      $output = $this->tokenService->replace($input, array(), array('langcode' => $this->languageInterface->id));
+      $output = $this->tokenService->replace($input, array(), array('langcode' => $this->languageInterface->getId()));
       $this->assertTrue($output == $expected, format_string('Token recognized in string %string', array('%string' => $input)));
     }
 
@@ -66,12 +66,12 @@ class TokenReplaceUnitTest extends TokenReplaceUnitTestBase {
 
     // Replace with with the clear parameter, only the valid token should remain.
     $target = String::checkPlain(\Drupal::config('system.site')->get('name'));
-    $result = $this->tokenService->replace($source, array(), array('langcode' => $this->languageInterface->id, 'clear' => TRUE));
+    $result = $this->tokenService->replace($source, array(), array('langcode' => $this->languageInterface->getId(), 'clear' => TRUE));
     $this->assertEqual($target, $result, 'Valid tokens replaced while invalid tokens ignored.');
 
     $target .= '[user:name]';
     $target .= '[bogus:token]';
-    $result = $this->tokenService->replace($source, array(), array('langcode' => $this->languageInterface->id));
+    $result = $this->tokenService->replace($source, array(), array('langcode' => $this->languageInterface->getId()));
     $this->assertEqual($target, $result, 'Valid tokens replaced while invalid tokens ignored.');
   }
 
@@ -111,7 +111,7 @@ class TokenReplaceUnitTest extends TokenReplaceUnitTestBase {
     $this->assertFalse(in_array(0, array_map('strlen', $tests)), 'No empty tokens generated.');
 
     foreach ($tests as $input => $expected) {
-      $output = $this->tokenService->replace($input, array(), array('langcode' => $this->languageInterface->id));
+      $output = $this->tokenService->replace($input, array(), array('langcode' => $this->languageInterface->getId()));
       $this->assertEqual($output, $expected, format_string('Sanitized system site information token %token replaced.', array('%token' => $input)));
     }
 
@@ -120,7 +120,7 @@ class TokenReplaceUnitTest extends TokenReplaceUnitTestBase {
     $tests['[site:slogan]'] = $config->get('slogan');
 
     foreach ($tests as $input => $expected) {
-      $output = $this->tokenService->replace($input, array(), array('langcode' => $this->languageInterface->id, 'sanitize' => FALSE));
+      $output = $this->tokenService->replace($input, array(), array('langcode' => $this->languageInterface->getId(), 'sanitize' => FALSE));
       $this->assertEqual($output, $expected, format_string('Unsanitized system site information token %token replaced.', array('%token' => $input)));
     }
 
@@ -146,18 +146,18 @@ class TokenReplaceUnitTest extends TokenReplaceUnitTestBase {
     // Generate and test tokens.
     $tests = array();
     $date_service = \Drupal::service('date');
-    $tests['[date:short]'] = $date_service->format($date, 'short', '', NULL, $this->languageInterface->id);
-    $tests['[date:medium]'] = $date_service->format($date, 'medium', '', NULL, $this->languageInterface->id);
-    $tests['[date:long]'] = $date_service->format($date, 'long', '', NULL, $this->languageInterface->id);
-    $tests['[date:custom:m/j/Y]'] = $date_service->format($date, 'custom', 'm/j/Y', NULL, $this->languageInterface->id);
-    $tests['[date:since]'] = $date_service->formatInterval(REQUEST_TIME - $date, 2, $this->languageInterface->id);
+    $tests['[date:short]'] = $date_service->format($date, 'short', '', NULL, $this->languageInterface->getId());
+    $tests['[date:medium]'] = $date_service->format($date, 'medium', '', NULL, $this->languageInterface->getId());
+    $tests['[date:long]'] = $date_service->format($date, 'long', '', NULL, $this->languageInterface->getId());
+    $tests['[date:custom:m/j/Y]'] = $date_service->format($date, 'custom', 'm/j/Y', NULL, $this->languageInterface->getId());
+    $tests['[date:since]'] = $date_service->formatInterval(REQUEST_TIME - $date, 2, $this->languageInterface->getId());
     $tests['[date:raw]'] = Xss::filter($date);
 
     // 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 = $this->tokenService->replace($input, array('date' => $date), array('langcode' => $this->languageInterface->id));
+      $output = $this->tokenService->replace($input, array('date' => $date), array('langcode' => $this->languageInterface->getId()));
       $this->assertEqual($output, $expected, format_string('Date token %token replaced.', array('%token' => $input)));
     }
   }
diff --git a/core/modules/taxonomy/lib/Drupal/taxonomy/Tests/TermLanguageTest.php b/core/modules/taxonomy/lib/Drupal/taxonomy/Tests/TermLanguageTest.php
index 0e44497..3da8b1b 100644
--- a/core/modules/taxonomy/lib/Drupal/taxonomy/Tests/TermLanguageTest.php
+++ b/core/modules/taxonomy/lib/Drupal/taxonomy/Tests/TermLanguageTest.php
@@ -103,10 +103,10 @@ function testDefaultTermLanguage() {
     // Change the default language of the site and check if the default terms
     // language is still correctly selected.
     $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);
     $edit = array(
       'default_language[langcode]' => 'site_default',
diff --git a/core/modules/views/lib/Drupal/views/Plugin/views/wizard/WizardPluginBase.php b/core/modules/views/lib/Drupal/views/Plugin/views/wizard/WizardPluginBase.php
index 4ed08e4..c31217f 100644
--- a/core/modules/views/lib/Drupal/views/Plugin/views/wizard/WizardPluginBase.php
+++ b/core/modules/views/lib/Drupal/views/Plugin/views/wizard/WizardPluginBase.php
@@ -634,7 +634,7 @@
       'label' => $form_state['values']['label'],
       'description' => $form_state['values']['description'],
       'base_table' => $this->base_table,
-      'langcode' => language_default()->id,
+      'langcode' => language_default()->getId(),
     );
 
     $view = entity_create('view', $values);
diff --git a/core/tests/Drupal/Tests/Core/Utility/TokenTest.php b/core/tests/Drupal/Tests/Core/Utility/TokenTest.php
index f92502e..be79860 100644
--- a/core/tests/Drupal/Tests/Core/Utility/TokenTest.php
+++ b/core/tests/Drupal/Tests/Core/Utility/TokenTest.php
@@ -83,7 +83,7 @@ class TokenTest extends UnitTestCase {
     );
 
     $language = $this->getMock('\Drupal\Core\Language\Language');
-    $language->id = $this->randomName();
+    $language->setId($this->randomName());
 
     $this->languageManager->expects($this->once())
       ->method('getCurrentLanguage')