Java: avoid checking for null in nested classes (Deep Null checking)

You can use for:

product.getLatestVersion().getProductData().getTradeItem().getInformationProviderOfTradeItem().getGln();

optional equivalent:

Optional.ofNullable(product).map(
            Product::getLatestVersion
        ).map(
            ProductVersion::getProductData
        ).map(
            ProductData::getTradeItem
        ).map(
            TradeItemType::getInformationProviderOfTradeItem
        ).map(
            PartyInRoleType::getGln
        ).orElse(null);