diff -u b/form_example/src/Forms/FormExampleTutorial.php b/form_example/src/Forms/FormExampleTutorial.php
--- b/form_example/src/Forms/FormExampleTutorial.php
+++ b/form_example/src/Forms/FormExampleTutorial.php
@@ -6,6 +6,7 @@
 namespace Drupal\form_example\Forms;
 
 use Drupal\Core\Form\FormBase;
+use Drupal\Core\Form\FormStateInterface;
 
 /**
  * This first form function is from the @link http://drupal.org/node/717722 Form Tutorial handbook page @endlink
@@ -30,7 +31,7 @@
   /**
    * {@inheritdoc}
    */
-  public function buildForm(array $form, array &$form_state) {
+  public function buildForm(array $form, FormStateInterface $form_state) {
 
     $form['description'] = array(
       '#type' => 'item',
@@ -50,8 +51,8 @@
    */
-  public function validateForm(array &$form, array &$form_state) {}
+  public function validateForm(array &$form, FormStateInterface $form_state) {}
 
   /**
    * {@inheritdoc}
    */
-  public function submitForm(array &$form, array &$form_state) {}
+  public function submitForm(array &$form, FormStateInterface $form_state) {}
 }
diff -u b/form_example/src/Forms/FormExampleTutorial10.php b/form_example/src/Forms/FormExampleTutorial10.php
--- b/form_example/src/Forms/FormExampleTutorial10.php
+++ b/form_example/src/Forms/FormExampleTutorial10.php
@@ -5,11 +5,10 @@
  */
 namespace Drupal\form_example\Forms;
 
-
-
 use Drupal\Core\Form\FormBase;
 use Drupal\file\Entity\File;
 use Drupal\file\FileInterface;
+use Drupal\Core\Form\FormStateInterface;
 
 
 
@@ -35,7 +34,7 @@
   /**
    * {@inheritdoc}
    */
-  public function buildForm(array $form, array &$form_state) {
+  public function buildForm(array $form, FormStateInterface $form_state) {
 
     // If you are familiar with how browsers handle files, you know that
     // enctype="multipart/form-data" is required. Drupal takes care of that, so
@@ -61,7 +60,7 @@
      * Validate function for form_example_tutorial_10().
      *
      */
-  public function validateForm(array &$form, array &$form_state)  {
+  public function validateForm(array &$form, FormStateInterface $form_state)  {
 
       $file = file_save_upload('file', array(
         // Validates file is really an image.
@@ -82,18 +81,18 @@
         }
         else {
         ;
-            $this->setFormError('file', $form_state, t("Failed to write the uploaded file to the site's file folder."));
+          $form_state->setErrorByName('file', t("Failed to write the uploaded file to the site's file folder."));
         }
       }
       else {
-        $this->setFormError('file', $form_state, t('No file was uploaded.'));
+        $form_state->setErrorByName('file', t('No file was uploaded.'));
       }
   }
 
   /**
    * {@inheritdoc}
    */
-  public function submitForm(array &$form, array &$form_state) {
+  public function submitForm(array &$form, FormStateInterface $form_state) {
     $file = $form_state['storage']['file'];
     // We are done with the file, remove it from storage.
 
diff -u b/form_example/src/Forms/FormExampleTutorial2.php b/form_example/src/Forms/FormExampleTutorial2.php
--- b/form_example/src/Forms/FormExampleTutorial2.php
+++ b/form_example/src/Forms/FormExampleTutorial2.php
@@ -6,6 +6,8 @@
 namespace Drupal\form_example\Forms;
 
 use Drupal\Core\Form\FormBase;
+use Drupal\Core\Form\FormStateInterface;
+
 
 /**
  * This is Example 2, a basic form with a submit button.
@@ -25,7 +27,7 @@
   /**
    * {@inheritdoc}
    */
-  public function buildForm(array $form, array &$form_state) {
+  public function buildForm(array $form, FormStateInterface $form_state) {
 
     $form['description'] = array(
       '#type' => 'item',
@@ -52,8 +54,8 @@
    */
-  public function validateForm(array &$form, array &$form_state) {}
+  public function validateForm(array &$form, FormStateInterface $form_state) {}
 
   /**
    * {@inheritdoc}
    */
-  public function submitForm(array &$form, array &$form_state) {}
+  public function submitForm(array &$form, FormStateInterface $form_state) {}
 }
diff -u b/form_example/src/Forms/FormExampleTutorial3.php b/form_example/src/Forms/FormExampleTutorial3.php
--- b/form_example/src/Forms/FormExampleTutorial3.php
+++ b/form_example/src/Forms/FormExampleTutorial3.php
@@ -6,6 +6,8 @@
 namespace Drupal\form_example\Forms;
 
 use Drupal\Core\Form\FormBase;
+use Drupal\Core\Form\FormStateInterface;
+
 
 /**
  * Example 3: A basic form with fieldsets.
@@ -32,7 +34,7 @@
   /**
    * {@inheritdoc}
    */
-  public function buildForm(array $form, array &$form_state) {
+  public function buildForm(array $form, FormStateInterface $form_state) {
     $form['description'] = array(
       '#type' => 'item',
       '#title' => t('A form with a fieldset'),
@@ -76,8 +78,8 @@
    */
-  public function validateForm(array &$form, array &$form_state) {}
+  public function validateForm(array &$form, FormStateInterface $form_state) {}
 
   /**
    * {@inheritdoc}
    */
-  public function submitForm(array &$form, array &$form_state) {}
+  public function submitForm(array &$form, FormStateInterface $form_state) {}
 }
diff -u b/form_example/src/Forms/FormExampleTutorial4.php b/form_example/src/Forms/FormExampleTutorial4.php
--- b/form_example/src/Forms/FormExampleTutorial4.php
+++ b/form_example/src/Forms/FormExampleTutorial4.php
@@ -6,6 +6,7 @@
 namespace Drupal\form_example\Forms;
 
 use Drupal\Core\Form\FormBase;
+use Drupal\Core\Form\FormStateInterface;
 
 /**
  * Example 4: Basic form with required fields.
@@ -24,7 +25,7 @@
   /**
    * {@inheritdoc}
    */
-  public function buildForm(array $form, array &$form_state) {
+  public function buildForm(array $form, FormStateInterface $form_state) {
     $form['description'] = array(
       '#type' => 'item',
       '#title' => t('A form with required fields'),
@@ -68,8 +69,8 @@
    */
-  public function validateForm(array &$form, array &$form_state) {}
+  public function validateForm(array &$form, FormStateInterface $form_state) {}
 
   /**
    * {@inheritdoc}
    */
-  public function submitForm(array &$form, array &$form_state) {}
+  public function submitForm(array &$form, FormStateInterface $form_state) {}
 }
diff -u b/form_example/src/Forms/FormExampleTutorial5.php b/form_example/src/Forms/FormExampleTutorial5.php
--- b/form_example/src/Forms/FormExampleTutorial5.php
+++ b/form_example/src/Forms/FormExampleTutorial5.php
@@ -6,6 +6,7 @@
 namespace Drupal\form_example\Forms;
 
 use Drupal\Core\Form\FormBase;
+use Drupal\Core\Form\FormStateInterface;
 
 /**
  * Example 5: Basic form with additional element attributes.
@@ -31,7 +32,7 @@
   /**
    * {@inheritdoc}
    */
-  public function buildForm(array $form, array &$form_state) {
+  public function buildForm(array $form, FormStateInterface $form_state) {
     $form['description'] = array(
       '#type' => 'item',
       '#title' => t('A form with additional attributes'),
@@ -79,8 +80,8 @@
    */
-  public function validateForm(array &$form, array &$form_state) {}
+  public function validateForm(array &$form, FormStateInterface $form_state) {}
 
   /**
    * {@inheritdoc}
    */
-  public function submitForm(array &$form, array &$form_state) {}
+  public function submitForm(array &$form, FormStateInterface $form_state) {}
 }
diff -u b/form_example/src/Forms/FormExampleTutorial6.php b/form_example/src/Forms/FormExampleTutorial6.php
--- b/form_example/src/Forms/FormExampleTutorial6.php
+++ b/form_example/src/Forms/FormExampleTutorial6.php
@@ -6,6 +6,7 @@
 namespace Drupal\form_example\Forms;
 
 use Drupal\Core\Form\FormBase;
+use Drupal\Core\Form\FormStateInterface;
 
 /**
  * Example 6: A basic form with a validate handler.
@@ -24,7 +25,7 @@
   /**
    * {@inheritdoc}
    */
-  public function buildForm(array $form, array &$form_state) {
+  public function buildForm(array $form, FormStateInterface $form_state) {
     $form['description'] = array(
       '#type' => 'item',
       '#title' => t('A form with a validation handler'),
@@ -84,13 +85,13 @@
    */
-  public function validateForm(array &$form, array &$form_state) {
+  public function validateForm(array &$form, FormStateInterface $form_state) {
     $year_of_birth = $form_state['values']['year_of_birth'];
     if ($year_of_birth && ($year_of_birth < 1900 || $year_of_birth > 2000)) {
-      $this->setFormError('year_of_birth', $form_state, t('Enter a year between 1900 and 2000.'));
-      }
+      $form_state->setErrorByName('year_of_birth', t('Enter a year between 1900 and 2000.'));
+    }
   }
 
   /**
    * {@inheritdoc}
    */
-  public function submitForm(array &$form, array &$form_state) {}
+  public function submitForm(array &$form, FormStateInterface $form_state) {}
 }
diff -u b/form_example/src/Forms/FormExampleTutorial7.php b/form_example/src/Forms/FormExampleTutorial7.php
--- b/form_example/src/Forms/FormExampleTutorial7.php
+++ b/form_example/src/Forms/FormExampleTutorial7.php
@@ -6,6 +6,7 @@
 namespace Drupal\form_example\Forms;
 
 use Drupal\Core\Form\FormBase;
+use Drupal\Core\Form\FormStateInterface;
 
 /**
  * Example 7: A basic form with a validate handler.
@@ -24,7 +25,7 @@
   /**
    * {@inheritdoc}
    */
-  public function buildForm(array $form, array &$form_state) {
+  public function buildForm(array $form, FormStateInterface $form_state) {
     $form['description'] = array(
       '#type' => 'item',
       '#title' => t('A form with a validation handler'),
@@ -83,20 +84,20 @@
    * function. An alternate list of validation functions could have been provided
    * in $form['#validate'].
    */
-  public function validateForm(array &$form, array &$form_state) {
+  public function validateForm(array &$form, FormStateInterface $form_state) {
 
 
       $year_of_birth = $form_state['values']['year_of_birth'];
       // Validate birthday year
       if ($year_of_birth && ($year_of_birth < 1900 || $year_of_birth > 2000)) {
-        $this->setFormError('year_of_birth', $form_state, t('Enter a year between 1900 and 2000.'));
+        $form_state->setErrorByName('year_of_birth', t('Enter a year between 1900 and 2000.'));
       }
   }
 
   /**
    * {@inheritdoc}
    */
-  public function submitForm(array &$form, array &$form_state) {
+  public function submitForm(array &$form, FormStateInterface $form_state) {
     if ($form_state['values']['op'] == t('Submit')) {
       drupal_set_message(t('The form has been submitted. name="@first @last", year of birth=@year_of_birth',
       array('@first' => $form_state['values']['first'], '@last' => $form_state['values']['last'], '@year_of_birth' => $form_state['values']['year_of_birth'])));
diff -u b/form_example/src/Forms/FormExampleTutorial8.php b/form_example/src/Forms/FormExampleTutorial8.php
--- b/form_example/src/Forms/FormExampleTutorial8.php
+++ b/form_example/src/Forms/FormExampleTutorial8.php
@@ -6,6 +6,9 @@
 namespace Drupal\form_example\Forms;
 
 use Drupal\Core\Form\FormBase;
+use Drupal\Core\Form\FormStateInterface;
+
+
 /**
  * Example 8: A simple multistep form with a Next and a Back button.
  *
@@ -33,7 +36,7 @@
   /**
    * {@inheritdoc}
    */
-  public function buildForm(array $form, array &$form_state) {
+  public function buildForm(array $form, FormStateInterface $form_state) {
     if (empty($form_state['page_values'])) $form_state['page_values'] = array();
     if (empty($form_state['page_num'])) $form_state['page_num'] = 1;
     // Build different form fields based on the $form['page_num'] value
@@ -61,12 +64,12 @@
    * function. An alternate list of validation functions could have been provided
    * in $form['#validate'].
    */
-  public function validateForm(array &$form, array &$form_state) {
+  public function validateForm(array &$form, FormStateInterface $form_state) {
     if(!empty($form_state['page_num']) && $form_state['page_num'] == 1) {
       $year_of_birth = $form_state['values']['year_of_birth'];
       // Validate birthday year
       if ($year_of_birth && ($year_of_birth < 1900 || $year_of_birth > 2000)) {
-        $this->setFormError('year_of_birth', $form_state, t('Enter a year between 1900 and 2000.'));
+        $form_state->setErrorByName('year_of_birth', t('Enter a year between 1900 and 2000.'));
       }
     }
     // if (!empty($form_state['page_num']) && $form_state['page_num'] == 2) {}
@@ -75,7 +78,7 @@
   /**
    * {@inheritdoc}
    */
-  public function submitForm(array &$form, array &$form_state) {
+  public function submitForm(array &$form, FormStateInterface $form_state) {
     // Normally, some code would go here to alter the database with the data
     // collected from the form. Instead sets a message with drupal_set_message()
     // to validate that the code worked.
diff -u b/form_example/src/Forms/FormExampleTutorial9.php b/form_example/src/Forms/FormExampleTutorial9.php
--- b/form_example/src/Forms/FormExampleTutorial9.php
+++ b/form_example/src/Forms/FormExampleTutorial9.php
@@ -6,6 +6,8 @@
 namespace Drupal\form_example\Forms;
 
 use Drupal\Core\Form\FormBase;
+use Drupal\Core\Form\FormStateInterface;
+
 /**
  * Example 9: A form with a dynamically added new fields.
  *
@@ -32,7 +34,7 @@
   /**
    * {@inheritdoc}
    */
-  public function buildForm(array $form, array &$form_state) {
+  public function buildForm(array $form, FormStateInterface $form_state) {
     // We will have many fields with the same name, so we need to be able to
     // access the form hierarchically.
     $form['#tree'] = TRUE;
@@ -111,12 +113,12 @@
      * Adds logic to validate the form to check the validity of the new fields,
      * if they exist.
      */
-  public function validateForm(array &$form, array &$form_state) {
+  public function validateForm(array &$form, FormStateInterface $form_state) {
     for ($i = 1; $i <= $form_state['num_names']; $i++) {
       $year_of_birth = $form_state['values']['name'][$i]['year_of_birth'];
 
       if ($year_of_birth && ($year_of_birth < 1900 || $year_of_birth > 2000)) {
-          $this->setFormError("name][$i][year_of_birth", $form_state, t('Enter a year between 1900 and 2000.'));
+        $form_state->setErrorByName("name][$i][year_of_birth", t('Enter a year between 1900 and 2000.'));
       }
     }
   }
@@ -124,7 +126,7 @@
   /**
    * {@inheritdoc}
    */
-  public function submitForm(array &$form, array &$form_state) {
+  public function submitForm(array &$form, FormStateInterface $form_state) {
     $output = t("Form 9 has been submitted.");
     for ($i = 1; $i <= $form_state['num_names']; $i++) {
       $output .= t("@num: @first @last (@date)...",