Creating Custom forms in Drupal 8

Good morning, Its a sunday morning and I am starting the day with a little brush up on my drupal 8 knowledge.
I am going to make a custom form, in that form I will make few fields and get default values from the saved configuration. This configuration would be set from the form.
I would go on and make settings save in files which would make the configurations under version control.

• Step 1: Creating custom form( form API). Drupal has got a good documentation of form api, it gives you in detail information about how one can create custom forms.
  In the previous post we had created a custom module `hello_world`. To build a form in drupal 8 we use:

  <?php
   Drupal\Core\Form\FormBase;
   Drupal\Core\Form\FormStateInterface;

  I will make a new routing file so that the form comes on a page.
• Step 2:We will create another file which will contain call the class and logic for the form.
  File would come as `modules/hello_world/src/Form/HelloWorldForm.php`. First we declare the namespace, the other classes we want to use, and extend the FormBase class. We use to get code from some other classes, using the `use` PHP keyword and then the namespace, using the PSR-4 standard, which will autoload the classes in the files that correspond to these namespaces.

  <?php
  /*
   * @file
   * Contains \Drupal\hello_world\form\HelloWorldForms
   *
   */
  
  namespace Drupal\hello_world\Form;
  
  use Drupal\Core\Form\FormBase;
  use Drupal\Core\Form\FormStateInterface;
  
  
  class HelloWorldForms extends FormBase {
    /*
     * {@inhertdoc}
     *
     */
    public function getFormId() {
        return 'Hello_world_form';
    }
     /**
         * {@inheritdoc}
         */
        public function buildForm(array $form, FormStateInterface $form_state) {
  
          $form['candidate_name']['first_name'] = array(
          '#type' => 'textfield',
          '#title' => t('First Name:'),
          '#required' => TRUE,
          );
          $form['candidate_name']['last_name'] = array(
          '#type' => 'textfield',
          '#title' => t('Last Name:'),
          '#required' => TRUE,
          );
          $form['actions']['#type'] = 'actions';
          $form['actions']['submit'] = array(
          '#type' => 'submit',
          '#value' => $this->t('Save'),
          '#button_type' => 'primary',
          );
          return $form;
        }
  
      public function submitForm(array &$form, FormStateInterface $form_state) {
  
      }
    }

  I have not used the validateForm which is used for form validations and my submitForm function is also empty right now.
  Right now I have got a custom form which has been made on route `hello_world/form`. Which contains 2 textfields and a submit form.
  
  Next step is to make a default config that would be loaded in these fields.
  First name: Nitish
  Last name: Guleria
  Let us put this in next blog post.