Exercise: Inventory management
Your task is to implement the missing functions in the Inventory class. This is how those methods should work:
addProductshould add a product to the inventory and assign a producer to it,removeProductshould remove a product from the inventory and remove the producer,addSellershould add a seller to the sellers' collection,removeSellershould remove a seller from the sellers' collection,getProductsCountshould return the number of products in the inventory,hasProductshould returntrueif the inventory contains the given product,hasProductsshould returntrueif the inventory contains any products,getProducershould return the producer of the given product, ornullif the product is not in the inventory,produceInventoryDisplayshould return a string containing the inventory display in the following format:
Inventory:
Produced by: {producer}
Sellers: {sellers}Starting code:
class Inventory {
private val products = mutableListOf<Product>()
private val productIdToProducer =
mutableMapOf<String, String>()
private val sellers = mutableSetOf<String>()
fun addProduct(product: Product, producer: String) {
// TODO: Add product and assign producer
}
fun removeProduct(product: Product) {
// TODO: Remove product and producer
}
fun getProductsCount(): Int = TODO()
fun hasProduct(product: Product): Boolean = TODO()
fun hasProducts(): Boolean = TODO()
fun getProducer(product: Product): String? = TODO()
fun addSeller(seller: String) {
// TODO: Add seller
}
fun removeSeller(seller: String) {
// TODO: Remove seller
}
fun produceInventoryDisplay(): String {
var result = "Inventory:\n"
// TODO: For each product, print name, category, price
// in the format "{name} ({category}) - ${price}"
// and print the producer in the format
// "Produced by: {producer}"
// TODO: Print sellers in the format
// "Sellers: {sellers}"
return result
}
}
class Product(
val id: String,
val name: String,
val price: Double,
val category: String,
)
Once your solution is ready, the following code should work:
val inventory = Inventory()
println(inventory.hasProducts()) // false
val p1 = Product("P1", "Phone", 599.99, "Electronics")
val p2 = Product("P2", "Laptop", 1199.99, "Electronics")
val p3 = Product("P3", "Shirt", 29.99, "Clothing")
inventory.addProduct(p1, "TechCompany")
inventory.addProduct(p2, "TechCompany")
inventory.addProduct(p3, "ClothingCompany")
inventory.addSeller("Seller1")
inventory.addSeller("Seller2")
println(inventory.getProductsCount()) // 3
println(inventory.hasProduct(p1)) // true
println(inventory.hasProducts()) // true
println(inventory.getProducer(p1)) // TechCompany
println(inventory.produceInventoryDisplay())
// Inventory:
// Phone (Electronics) - $599.99
// Produced by: TechCompany
// Laptop (Electronics) - $1199.99
// Produced by: TechCompany
// Shirt (Clothing) - $29.99
// Produced by: ClothingCompany
// Sellers: [Seller1, Seller2]
inventory.removeProduct(p2)
inventory.addSeller("Seller1")
inventory.removeSeller("Seller2")
println(inventory.getProductsCount()) // 2
println(inventory.hasProduct(p1)) // true
println(inventory.hasProduct(p2)) // false
println(inventory.hasProducts()) // true
println(inventory.getProducer(p2)) // null
println(inventory.produceInventoryDisplay())
// Inventory:
// Phone (Electronics) - $599.99
// Produced by: TechCompany
// Shirt (Clothing) - $29.99
// Produced by: ClothingCompany
// Sellers: [Seller1]
This problem can either be solved in the below playground or you can clone kotlin-exercises project and solve it locally. In the project, you can find code template for this exercise in essentials/collections/Inventory.kt. You can find there starting code, example usage and unit tests.
Once you are done with the exercise, you can check your solution here.
Playground
import junit.framework.TestCase.*
import org.junit.Before
import org.junit.Test
import kotlin.test.assertEquals
class Inventory {
private val products = mutableListOf<Product>()
private val productIdToProducer =
mutableMapOf<String, String>()
private val sellers = mutableSetOf<String>()
fun addProduct(product: Product, producer: String) {
// TODO: Add product and assign producer
}
fun removeProduct(product: Product) {
// TODO: Remove product and producer
}
fun getProductsCount(): Int = TODO()
fun hasProduct(product: Product): Boolean = TODO()
fun hasProducts(): Boolean = TODO()
fun getProducer(product: Product): String? = TODO()
fun addSeller(seller: String) {
// TODO: Add seller
}
fun removeSeller(seller: String) {
// TODO: Remove seller
}
fun produceInventoryDisplay(): String {
var result = "Inventory:\n"
// TODO: For each product, print name, category, price
// in the format "{name} ({category}) - ${price}"
// and print the producer in the format
// "Produced by: {producer}"
// TODO: Print sellers in the format
// "Sellers: {sellers}"
return result
}
}
class Product(
val id: String,
val name: String,
val price: Double,
val category: String,
)
fun main() {
val inventory = Inventory()
println(inventory.hasProducts()) // false
val p1 = Product("P1", "Phone", 599.99, "Electronics")
val p2 = Product("P2", "Laptop", 1199.99, "Electronics")
val p3 = Product("P3", "Shirt", 29.99, "Clothing")
inventory.addProduct(p1, "TechCompany")
inventory.addProduct(p2, "TechCompany")
inventory.addProduct(p3, "ClothingCompany")
inventory.addSeller("Seller1")
inventory.addSeller("Seller2")
println(inventory.getProductsCount()) // 3
println(inventory.hasProduct(p1)) // true
println(inventory.hasProducts()) // true
println(inventory.getProducer(p1)) // TechCompany
println(inventory.produceInventoryDisplay())
// Inventory:
// Phone (Electronics) - $599.99
// Produced by: TechCompany
// Laptop (Electronics) - $1199.99
// Produced by: TechCompany
// Shirt (Clothing) - $29.99
// Produced by: ClothingCompany
// Sellers: [Seller1, Seller2]
inventory.removeProduct(p2)
inventory.addSeller("Seller1")
inventory.removeSeller("Seller2")
println(inventory.getProductsCount()) // 2
println(inventory.hasProduct(p1)) // true
println(inventory.hasProduct(p2)) // false
println(inventory.hasProducts()) // true
println(inventory.getProducer(p2)) // null
println(inventory.produceInventoryDisplay())
// Inventory:
// Phone (Electronics) - $599.99
// Produced by: TechCompany
// Shirt (Clothing) - $29.99
// Produced by: ClothingCompany
// Sellers: [Seller1]
}
class InventoryTest {
private lateinit var inventory: Inventory
private val apple = Product("1", "Apple", 0.5, "Fruit")
private var banana = Product("2", "Banana", 0.3, "Fruit")
@Before
fun setup() {
inventory = Inventory()
}
@Test
fun `addProduct should increase product count and set producer`() {
inventory.addProduct(apple, "FruitCorp")
assertEquals(1, inventory.getProductsCount())
assertTrue(inventory.hasProduct(apple))
assertEquals("FruitCorp", inventory.getProducer(apple))
}
@Test
fun `removeProduct should decrease product count and remove producer`() {
inventory.addProduct(apple, "FruitCorp")
inventory.removeProduct(apple)
assertEquals(0, inventory.getProductsCount())
assertFalse(inventory.hasProduct(apple))
assertNull(inventory.getProducer(apple))
}
@Test
fun `addSeller should add seller to the inventory`() {
inventory.addSeller("SellerA")
assertTrue(inventory.produceInventoryDisplay().contains("SellerA"))
}
@Test
fun `removeSeller should remove seller from the inventory`() {
inventory.addSeller("SellerA")
inventory.removeSeller("SellerA")
assertFalse(inventory.produceInventoryDisplay().contains("SellerA"))
}
@Test
fun `produceInventoryDisplay should display products and sellers correctly`() {
inventory.addProduct(apple, "FruitCorp")
inventory.addProduct(banana, "TropicalFruitCorp")
inventory.addSeller("SellerA")
inventory.addSeller("SellerB")
val expectedDisplay = """
Inventory:
Apple (Fruit) - 0.5
Produced by: FruitCorp
Banana (Fruit) - 0.3
Produced by: TropicalFruitCorp
Sellers: [SellerA, SellerB]
""".trimIndent()
assertEquals(expectedDisplay, inventory.produceInventoryDisplay())
}
@Test
fun `hasProducts should return true when there are products`() {
inventory.addProduct(apple, "FruitCorp")
assertTrue(inventory.hasProducts())
}
@Test
fun `hasProducts should return false when there are no products`() {
assertFalse(inventory.hasProducts())
}
@Test
fun `getProducer should return null for nonexistent product`() {
assertNull(inventory.getProducer(apple))
}
}
