While working on an e$-$commerce service, you need to build a simple aggregator for a report,

which will hold sold products and a sum of their prices converted to EUR currency.

You're given a stream $($java$.$util.stream.Stream$)$ of SoldProduct

objects. Sold Product is defined as follows:

@Value

class SoldProduct $\{$

String name;

BigDecimal price;

String currency:

$\}$

$($@Value comes from lombok tool and will make this class immutable $-$ generate toString, equals and hashCode, make all fields

private and final, add getters for all the fields and add single all arguments constructor$).$

Write a function, which will map the Stream Sold Product instance of Sold ProductsAggregate to an which is defined as follows:

@Value

class SoldProductsAggregate $\{$

List SimpleSold Product$>$ products;

BigDecimal total;

and SimpleSoldProduct:

@Value

class SimpleSoldProduct $\{$

String name;

BigDecimal price;

$\}$

To convert price to EUR use EURExchangeService which implements ExchangeService:

interface ExchangeService $\{$

Optional rate$($String currency$)$;

$\}$

Unfortunately EURExchangeService is

a bit buggy and may return some invalid values $($like null, empty or negative$).$ You should handle it by ignoring them.?

If an argument you get as input to SoldProductsAggregate.aggregate$()$

is null, empty Stream

and so on$-$then you must not return null In case of such argument vou must convert it to empty Stream Before doing the mapping