Laravel: ReflectionException - Class App\Http\Controllers\XXXX does not exist

I am trying to run test page using Laravel.

When I use Controller, every time I got message:

Laravel: ReflectionException - Class App\Http\Controllers\XXXX does not exist

Does somebody knows where problem is?

This is my routes/web.php:

   Route::get('/hi', 'HiController@index');

HiController.php (it is in correct folder structure: app/Http/Controllers/

namespace App\Http\Controllers;

use Illuminate\Http\Request;

class HiController extends Controller
{
    public function index(){
      return "test";
    }
}

RouteServiceProvider.php

namespace App\Providers;

use Illuminate\Support\Facades\Route;
use Illuminate\Foundation\Support\Providers\RouteServiceProvider as ServiceProvider;

class RouteServiceProvider extends ServiceProvider
{
    /**
     * This namespace is applied to your controller routes.
     *
     * In addition, it is set as the URL generator's root namespace.
     *
     * @var string
     */
    protected $namespace = 'App\Http\Controllers';

    /**
     * Define your route model bindings, pattern filters, etc.
     *
     * @return void
     */
    public function boot()
    {
        //

        parent::boot();
    }

    /**
     * Define the routes for the application.
     *
     * @return void
     */
    public function map()
    {
        $this->mapApiRoutes();

        $this->mapWebRoutes();

        //
    }

    /**
     * Define the "web" routes for the application.
     *
     * These routes all receive session state, CSRF protection, etc.
     *
     * @return void
     */
    protected function mapWebRoutes()
    {
        Route::middleware('web')
             ->namespace($this->namespace)
             ->group(base_path('routes/web.php'));
    }

    /**
     * Define the "api" routes for the application.
     *
     * These routes are typically stateless.
     *
     * @return void
     */
    protected function mapApiRoutes()
    {
        Route::prefix('api')
             ->middleware('api')
             ->namespace($this->namespace)
             ->group(base_path('routes/api.php'));
    }
}

Also, when I use this code in routes/web.php it works:

Route::get('/hi', function (){
  return "hi";
});

It's clean Laravel 5.6 installation, on Windows, wamp64.

I tried also with "composer dump auto-load" and "php artisan config:clear" but nothing works.

Thank you in advance.

via Chebli Mohamed