use GuzzleHttp\ClientInterface;
/**
 * An http client.
 *
 * @var \GuzzleHttp\ClientInterface
 */
protected $httpClient;
 /**
 * The form constructor.
 *
 * @param \GuzzleHttp\ClientInterface $http_client
 *   Guzzle client interface.
 */
public 

$external_file = 'https://www.example.com/test.png'
$destination = 'sites/default/files/test.png';
$response = \Drupal::httpClient()->get($external_file, ['sink' => $destination]);

Get file URL without domain /sites/default/files/import-xml/export_w0h_2.xml

$file = $this->entityTypeManager->getStorage('file')->load($fid);
$file_url = $file->createFileUrl();

Get file URL with domain and protocol

$file_url = $file->createFileUrl(FALSE);

/**
 * The entity type manager.
 *
 * @var \Drupal\Core\Entity\EntityTypeManagerInterface
 */
protected $entityTypeManager;
/**
 * The form constructor.
 *
 * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
 *   The entity type manager.
 */
public function 

drush entity:delete node --bundle=product

drush entity:delete taxonomy_term --bundle=application

$this->t('April', [], ['context' => 'Long month name']),

$response = new TrustedRedirectResponse('https://google.com');
$form_state->setResponse($response);

/**
* Implements hook_local_tasks_alter().
*/
function EXAMPLE_local_tasks_alter(&$local_tasks) {
 unset($local_tasks['user.register']);
}

$route_name = \Drupal::routeMatch()->getRouteName();