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.SoldProduct 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 contructor$).$

Write a function,Which will map the Stream to an instance of SoldProductsAggregate which is defined as

follows:

@Value

class SoldProductsAggregate

$\{$

List 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 be return some invalid values$($like null,empty or negative$).$

You should handle it by ignoring them.

If an argumemt you get as input to

SoldProductsAggregates.aggregate$()$ is null,empty Stream and so on$-$thenyou must not return null.In case of such argument,

you must convert it to empty Stream before doing the mapping.