target class 5bcontroller 5d does not exist

1//accessing any function in the controller (this is web.php file)
2use App\Http\Controllers\PostsController;
3
4Route::get('/post', 'App\Http\Controllers\PostsController@index');

1use App\Http\Controllers\UserController;
2
3Route::get('/users', [UserController::class, 'index']);
4// or
5Route::get('/users', 'App\Http\Controllers\UserController@index');
6

1//In laravel 8 uncomment  protected $namespace='App\\Http\\Controllers';

1
2Route::get('/users', [UserController::class, 'index']);

1[PagesController::class, 'index']