Update stock item quantity for a product in magento

Here is the useful code for a purpose : update stock item quantity for a product in magento: $product = Mage::getModel(‘catalog/product’)->load($productId); if ($product){ if (!($stockItem = $product->getStockItem())) { $stockItem = Mage::getModel(‘cataloginventory/stock_item’); $stockItem->assignProduct($product); } $stockItem->setData(‘qty’,intval($qty)) ->setData(‘is_in_stock’, intval($qty) > 0 ? 1 : 0) ->setData(‘manage_stock’, 1) ->setData(‘use_config_manage_stock’, 0) ->save(); }    

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