diff --git a/1ano/2semestre/poo/src/aula08/ex3/Interfaces/IProduct.java b/1ano/2semestre/poo/src/aula08/ex3/Interfaces/IProduct.java
new file mode 100644
index 0000000..976274b
--- /dev/null
+++ b/1ano/2semestre/poo/src/aula08/ex3/Interfaces/IProduct.java
@@ -0,0 +1,10 @@
+package aula08.ex3.Interfaces;
+
+public interface IProduct {
+    String getName();
+    void setPrice(double price);
+    double getPrice();
+    int stock();
+    void addStock(int amount);
+    void removeStock(int amount);
+}
diff --git a/1ano/2semestre/poo/src/aula08/ex3/Interfaces/IPurchase.java b/1ano/2semestre/poo/src/aula08/ex3/Interfaces/IPurchase.java
new file mode 100644
index 0000000..f9a007c
--- /dev/null
+++ b/1ano/2semestre/poo/src/aula08/ex3/Interfaces/IPurchase.java
@@ -0,0 +1,9 @@
+package aula08.ex3.Interfaces;
+
+import aula08.ex3.Product;
+
+public interface IPurchase {
+    void addProduct(Product product, int amount);
+    void listProducts();
+    double getTotal();
+}
diff --git a/1ano/2semestre/poo/src/aula08/ex3/Product.java b/1ano/2semestre/poo/src/aula08/ex3/Product.java
new file mode 100644
index 0000000..03ed778
--- /dev/null
+++ b/1ano/2semestre/poo/src/aula08/ex3/Product.java
@@ -0,0 +1,52 @@
+package aula08.ex3;
+
+import aula08.ex3.Interfaces.IProduct;
+
+public class Product implements IProduct {
+    private final String name;
+    private double price;
+    private int stock = 0;
+
+    public Product(String name, double price, int stock) {
+        this.name = name;
+        this.setPrice(price);
+        this.addStock(stock);
+    }
+
+    @Override
+    public String getName() {
+        return this.name;
+    }
+
+    @Override
+    public double getPrice() {
+        return this.price;
+    }
+
+    @Override
+    public void setPrice(double price) {
+        if (price <= 0)
+            throw new IllegalArgumentException("Price must be positive.");
+        this.price = price;
+    }
+
+    @Override
+    public int stock() {
+        return this.stock;
+    }
+
+    @Override
+    public void addStock(int amount) {
+        this.stock += amount;
+    }
+
+    @Override
+    public void removeStock(int amount) {
+        this.stock -= amount;
+    }
+
+    @Override
+    public String toString() {
+        return String.format("Product: %s\n\tStock: %d\n\tPrice: %.2f\n", this.getName(), this.stock(), this.getPrice());
+    }
+}
diff --git a/1ano/2semestre/poo/src/aula08/ex3/ProductWithDiscount.java b/1ano/2semestre/poo/src/aula08/ex3/ProductWithDiscount.java
new file mode 100644
index 0000000..70e28e2
--- /dev/null
+++ b/1ano/2semestre/poo/src/aula08/ex3/ProductWithDiscount.java
@@ -0,0 +1,23 @@
+package aula08.ex3;
+
+public class ProductWithDiscount extends Product {
+    private double discountPercentage;
+
+    public ProductWithDiscount(String name, double price, int stock, double discountPercentage) {
+        super(name, price, stock);
+        this.discountPercentage = discountPercentage;
+    }
+
+    public double getDiscountPercentage() {
+        return this.discountPercentage;
+    }
+
+    public void setDiscountPercentage(double discountPercentage) {
+        this.discountPercentage = discountPercentage;
+    }
+
+    @Override
+    public double getPrice() {
+        return super.getPrice() * (1 - discountPercentage / 100);
+    }
+}
diff --git a/1ano/2semestre/poo/src/aula08/ex3/Purchase.java b/1ano/2semestre/poo/src/aula08/ex3/Purchase.java
new file mode 100644
index 0000000..d6a1afb
--- /dev/null
+++ b/1ano/2semestre/poo/src/aula08/ex3/Purchase.java
@@ -0,0 +1,36 @@
+package aula08.ex3;
+
+import aula08.ex3.Interfaces.IPurchase;
+import java.util.LinkedHashMap;
+
+public class Purchase implements IPurchase {
+    private final LinkedHashMap<Product, Integer> products = new LinkedHashMap<>();
+
+    @Override
+    public void addProduct(Product product, int amount) {
+        if (product.stock() < amount)
+            amount = product.stock();
+        product.removeStock(amount);
+        if (products.containsKey(product)) {
+            int currentAmount = products.get(product);
+            products.replace(product, currentAmount+amount);
+        } else
+            products.put(product, amount);
+    }
+
+    @Override
+    public void listProducts() {
+        for (Product product : products.keySet()) {
+            int productAmount = products.get(product);
+            System.out.printf("Product: %s\n\tAmount: %d\n\tPrice: %.2f\n", product.getName(), productAmount, productAmount * product.getPrice());
+        }
+    }
+
+    @Override
+    public double getTotal() {
+        double total = 0;
+        for (Product product : products.keySet())
+            total += product.getPrice() * products.get(product);
+        return total;
+    }
+}
diff --git a/1ano/2semestre/poo/src/aula08/ex3/ShoppingCartTester.java b/1ano/2semestre/poo/src/aula08/ex3/ShoppingCartTester.java
index 522e606..f8ab88f 100644
--- a/1ano/2semestre/poo/src/aula08/ex3/ShoppingCartTester.java
+++ b/1ano/2semestre/poo/src/aula08/ex3/ShoppingCartTester.java
@@ -2,18 +2,18 @@ package aula08.ex3;
 
 public class ShoppingCartTester {
     public static void main(String[] args) {
-        /*Produto p1 = new ProdutoGenerico("Camisolas", 10, 3);
-        Produto p2 = new ProdutoGenerico("Calças", 30, 1);
-        Produto p3 = new ProdutoComDesconto("Sapatilhas", 50, 2, 50);
-        Produto p4 = new ProdutoComDesconto("Casacos", 100, 1, 10);
+        Product p1 = new Product("Camisolas", 10, 3);
+        Product p2 = new Product("Calças", 30, 1);
+        Product p3 = new ProductWithDiscount("Sapatilhas", 50, 2, 50);
+        Product p4 = new ProductWithDiscount("Casacos", 100, 1, 10);
         
-        CarrinhoDeCompras carrinho = new CarrinhoDeCompras();
-        carrinho.adicionarProduto(p1, 1);
-        carrinho.adicionarProduto(p2, 5);
-        carrinho.adicionarProduto(p3, 2);
-        carrinho.adicionarProduto(p4, 1);
+        Purchase compra = new Purchase();
+        compra.addProduct(p2, 5);
+        compra.addProduct(p3, 2);
+        compra.addProduct(p4, 1);
+        compra.addProduct(p1, 1);
 
-        carrinho.listarProdutos();
-        System.out.printf("Preço total da compra %.2f\n", carrinho.calcularTotal());*/
+        compra.listProducts();
+        System.out.printf("Preço total da compra %.2f\n", compra.getTotal());
     }
 }