$//$fill this out and make sure it works

$//$streamtest$.$java

package question$3$;

import java.util.stream.Stream;

public class StreamsTest $\{$

public static class Item $\{$

Double amount;

Integer count;

ItemType itemType;

public Item$($Double amount, Integer count, ItemType itemType$)\{$

this.amount $=$ amount;

this.count $=$ count;

this.itemType $=$ itemType;

$\}$

$\}$

$//$ question$3.$java

package question$3$;

import java.util.List;

import java.util.function.Function;

import java.util.stream.Collectors;

import org.testng.Assert;

import org.testng.annotations.Test;

public class Question$3\{$

$/*$

$*$ Create a stream method that returns the total amount for each item, filtered by item type

$*/$

@Test

public void test$()\{$

var item $=$ new StreamsTest.Item$(100\mathrm{.}0,2,$ StreamsTest.ItemType.RETURN$)$;

Assert.assertEquals$($StreamsTest$.$processStream$($

List.of$($item$).$stream$(),$ StreamsTest.ItemType.RETURN$)$

$.$mapToDouble$(($a $->$ a$)).$sum$(),200\mathrm{.}0)$;

var item$2=$ new StreamsTest.Item$(100\mathrm{.}0,3,$ StreamsTest.ItemType.RETURN$)$;

Assert.assertEquals$($StreamsTest$.$processStream$($

List.of$($item$,$ item$2).$stream$(),$ StreamsTest.ItemType.RETURN$)$

$.$mapToDouble$(($a $->$ a$)).$sum$(),500\mathrm{.}0)$;

Assert.assertEquals$($StreamsTest$.$processStream$($

List.of$($item$,$ item$2).$stream$(),$ StreamsTest.ItemType.PURCHASE$)$

$.$mapToDouble$(($a $->$ a$)).$sum$(),0\mathrm{.}0)$;

$\}$

$\}$