Laravel 8 (version 8.35.1): Target class does not exist - laravel

Question

I'm using laravel 8.35.1 version. I have a api-resource controller "ProductController". At my route file api.php. I define the route this:
api.php
<?php
use Illuminate\Http\Request;
use Illuminate\Support\Facades\Route;
Route::middleware('auth:api')->get('/user', function (Request $request) {
return $request->user();
});
Route::apiResource('/products', 'App\Http\Controllers\ProductController');
Route::group(['prefix' => 'products'], function () {
Route::apiResource('/{product}/review', 'App\Http\Controllers\ReviewController');
});
NOTE:
It's work fine but, when i remove the complete path of controller like just write Route::apiResource('/products', 'ProductController'); it show error
Target class [ProductController] does not exist.
Before first clearing the cache. I want to get rid of the complete path. and second want to place the controllers in Api folder, so how to define route for that also.
I have also tried ProductController::class but not work fine
Updated
when I use the route according the laravel 8 doc. https://laravel.com/docs/8.x/controllers#resource-controllers it is working fine. but when move the controller file to Api folder then declare the route name space like use App\Http\Controllers\Api\ProductController; show error again
<?php
use Illuminate\Http\Request;
use Illuminate\Support\Facades\Route;
use App\Http\Controllers\ProductController;
use App\Http\Controllers\ReviewController;
Route::middleware('auth:api')->get('/user', function (Request $request) {
return $request->user();
});
Route::apiResource('/products', ProductController::class);
Route::group(['prefix' => 'products'], function () {
Route::apiResource('/{products}/reviews', ReviewController::class);
});

Answer 1

You dont have to use class on declare controller in routing.
You may change 'ProductController' instead ProductController::class

Answer 2

When i try this then it work fine for me.
<?php
use Illuminate\Http\Request;
use Illuminate\Support\Facades\Route;
use App\Http\Controllers\ReviewController;
Route::middleware('auth:api')->get('/user', function (Request $request) {
return $request->user();
});
Route::apiResource('/products', 'App\Http\Controllers\ProductController');
Route::group(['prefix' => 'products'], function () {
Route::apiResource('/{product}/reviews', [ReviewController::class, 'ReviewController']);
});