Shopping cart implementation

src/main/java/com/example/shoppingcart/Product.java

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+package com.example.shoppingcart;
+
+public class Product {
+    private final String name;
+    private final double price;
+
+    public Product(String name, double price) {
+        this.name = name;
+        this.price = price;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public double getPrice() {
+        return price;
+    }
+}
+

src/main/java/com/example/shoppingcart/ShoppingCart.java

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+package com.example.shoppingcart;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class ShoppingCart {
+
+    private final Map<Product, Integer> items = new HashMap<>();
+    private double discount = 0.0;
+
+    public void addProduct(Product product, int quantity) {
+        items.merge(product, quantity, Integer::sum);
+    }
+
+    public void removeProduct(Product product) {
+        items.remove(product);
+    }
+
+    public Map<Product, Integer> getItems() {
+        return items;
+    }
+
+    public void applyDiscount(double discount) {
+        this.discount = discount;
+    }
+
+    public double calculateTotal() {
+        double total = 0.0;
+        for (Map.Entry<Product, Integer> entry : items.entrySet()) {
+            total += entry.getKey().getPrice() * entry.getValue();
+        }
+        return total * (1 - discount); // stöd för rabatt
+    }
+    public void updateQuantity(Product product, int newQuantity) {
+        if (newQuantity <= 0) {
+            items.remove(product);
+        } else {
+            items.put(product, newQuantity);
+        }
+    }
+
+}

src/test/java/com/example/shoppingcart/ShoppingCartTest.java

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+package com.example.shoppingcart;
+
+import org.junit.jupiter.api.Test;
+import static org.assertj.core.api.Assertions.*;
+
+public class ShoppingCartTest {
+
+    @Test
+    void shouldAddProductToCart() {
+        ShoppingCart cart = new ShoppingCart();
+        Product product = new Product("Apple", 10.0);
+
+        cart.addProduct(product, 1);
+
+        assertThat(cart.getItems()).containsEntry(product, 1);
+    }
+
+    @Test
+    void shouldRemoveProductFromCart() {
+        ShoppingCart cart = new ShoppingCart();
+        Product product = new Product("Banana", 5.0);
+
+        cart.addProduct(product, 2);
+        cart.removeProduct(product);
+
+        assertThat(cart.getItems()).doesNotContainKey(product);
+    }
+
+    @Test
+    void shouldCalculateTotalPrice() {
+        ShoppingCart cart = new ShoppingCart();
+        Product apple = new Product("Apple", 10.0);
+        Product banana = new Product("Banana", 5.0);
+
+        cart.addProduct(apple, 2);  // 2 x 10 = 20
+        cart.addProduct(banana, 3); // 3 x 5 = 15
+
+        double total = cart.calculateTotal();  // FIXAT HÄR
+
+        assertThat(total).isEqualTo(35.0);
+    }
+
+    @Test
+    void shouldApplyPercentageDiscountToTotalPrice() {
+        ShoppingCart cart = new ShoppingCart();
+        Product product1 = new Product("Apple", 10.0);
+        Product product2 = new Product("Banana", 5.0);
+
+        cart.addProduct(product1, 2); // 20 kr
+        cart.addProduct(product2, 4); // 20 kr
+        cart.applyDiscount(0.10); // 10% rabatt
+
+        double total = cart.calculateTotal();
+
+        assertThat(total).isEqualTo(36.0); // 40 - 10% = 36
+    }
+
+    @Test
+    void shouldCalculateTotalPriceWithNoDiscount() {
+        ShoppingCart cart = new ShoppingCart();
+        Product apple = new Product("Apple", 10.0);
+        Product banana = new Product("Banana", 5.0);
+
+        cart.addProduct(apple, 2);  // 20.0
+        cart.addProduct(banana, 3); // 15.0
+
+        double total = cart.calculateTotal();
+
+        assertThat(total).isEqualTo(35.0);
+    }
+    @Test
+    void shouldUpdateQuantityOfExistingProduct() {
+        ShoppingCart cart = new ShoppingCart();
+        Product apple = new Product("Apple", 10.0);
+
+        cart.addProduct(apple, 2);
+        cart.updateQuantity(apple, 5); // ändra direkt till 5
+
+        assertThat(cart.getItems()).containsEntry(apple, 5);
+    }
+    @Test
+    void shouldRemoveProductWhenQuantityIsZero() {
+        ShoppingCart cart = new ShoppingCart();
+        Product apple = new Product("Apple", 10.0);
+        cart.addProduct(apple, 2);
+
+        cart.updateQuantity(apple, 0);
+
+        assertThat(cart.getItems()).doesNotContainKey(apple);
+    }
+
+}