PayPalPaymentServiceV2.java

//...

@Override
@SneakyThrows
public CreatedOrder createOrder(Double totalAmount, URI returnUrl) {
    final OrderRequest orderRequest = createOrderRequest(totalAmount, returnUrl);
    final OrdersCreateRequest ordersCreateRequest = new OrdersCreateRequest().requestBody(orderRequest);
    final HttpResponse<Order> orderHttpResponse = payPalHttpClient.execute(ordersCreateRequest);
    final Order order = orderHttpResponse.result();
    LinkDescription approveUri = extractApprovalLink(order);
    return new CreatedOrder(order.id(),URI.create(approveUri.href()));
}

private OrderRequest createOrderRequest(Double totalAmount, URI returnUrl) {
    final OrderRequest orderRequest = new OrderRequest();
    setCheckoutIntent(orderRequest);
    setPurchaseUnits(totalAmount, orderRequest);
    setApplicationContext(returnUrl, orderRequest);
    return orderRequest;
}

private OrderRequest setApplicationContext(URI returnUrl, OrderRequest orderRequest) {
    return orderRequest.applicationContext(new ApplicationContext().returnUrl(returnUrl.toString()));
}

private void setPurchaseUnits(Double totalAmount, OrderRequest orderRequest) {
    final PurchaseUnitRequest purchaseUnitRequest = new PurchaseUnitRequest()
            .amountWithBreakdown(new AmountWithBreakdown().currencyCode("USD").value(totalAmount.toString()));
    orderRequest.purchaseUnits(Arrays.asList(purchaseUnitRequest));
}

private void setCheckoutIntent(OrderRequest orderRequest) {
    orderRequest.checkoutPaymentIntent("CAPTURE");
}

private LinkDescription extractApprovalLink(Order order) {
    LinkDescription approveUri = order.links().stream()
            .filter(link -> APPROVE_LINK_REL.equals(link.rel()))
            .findFirst()
            .orElseThrow(NoSuchElementException::new);
    return approveUri;
}

//...