Target class does not exist. code example

Example 1: Target class [] does not exist.

composer dump-autoload

Example 2: Target class [Controller] does not exist.

//accessing any function in the controller (this is web.php file)
use App\Http\Controllers\PostsController;

Route::get('/post', 'App\Http\Controllers\PostsController@index');

Example 3: Target class does not exist.

use App\Http\Controllers\UserController;

Route::get('/users', [UserController::class, 'index']);
// or
Route::get('/users', 'App\Http\Controllers\UserController@index');

Example 4: Target class [Controller] does not exist.

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

Example 5: Target class [ExamSeeder] does not exist.

php composer dump-autoload
php artisan migrate:refresh --seed