How we can Url Alias in Drupal 8?

If you want to path alias in drupal 8 then we have different syntax in drupal 8, Please follow this.
Syntax:
$alias = \Drupal::service('path.alias_manager')->getAliasByPath($tid or $nid);

Example: like if we have taxonomy term and we want to path alias so first we create URL path as given exmaple..

$tid = '/taxonomy/term/'.$term_id;
$alias = \Drupal::service('path.alias_manager')->getAliasByPath($tid); or \Drupal::service('path.alias_manager')->getAliasByPath('/taxonomy/term/'.$term_id),

OR

$nid = '/node/'.$node_id;
$alias = \Drupal::service('path.alias_manager')->getAliasByPath($nid); or \Drupal::service('path.alias_manager')->getAliasByPath('/node/'.$node_id),


Simple then we can use this alias to send or redirect using
$response = new Symfony\Component\HttpFoundation\RedirectResponse($alias);
$response->send();
return; 


Note: If have any suggestions or issue regarding 'How we can Url Alias in Drupal 8?' then you can ask by comments.

Page Redirection programmatically in drupal 8.

In drupal 8 for page redirection, we have to use Symfony components class. Here page redirection is done by 'RedirectResponse' class from Symfony HttpFoundation. In drupal 7 we using drupal_goto() function for redirect.
But in case of drupal 8, RedirectResponse' class is..

use Symfony\Component\HttpFoundation\RedirectResponse;

and suppose redirection page is node 2691 so we will give redirect url is '/node/2691'.
Example:
$url = '/node/2691';
return new RedirectResponse($url);

               OR

$redirect_variable = new Symfony\Component\HttpFoundation\RedirectResponse('/node/2691');     $redirect_variable ->send();
 return;

     For front page redirection, we can use..

return new \Symfony\Component\HttpFoundation\RedirectResponse(\Drupal::url('<front>'));

             OR
 In Function we can use redirect..
 public function submitForm(array &$form, FormStateInterface $form_state) {
   $form_state->setRedirect('redirect router name');
Example:
  $form_state->setRedirect('account_login.content');
 }

Note: If have any suggestions or issue regarding 'Page Redirection programmatically in drupal 8' then you can ask by comments.