Fixed the way the read-only lists and maps are returned from the Menu and OrderImpl classes.

Author: ProgrammingKiddo

src/main/java/coreapi/Menu.java

@@ -56,7 +56,7 @@ public float getPrice()
 	 */
 	public List<Product> getProductsInMenu()
 	{
-		return Collections.unmodifiableList(new ArrayList<Product>(productsMenu.keySet()));
+		return List.copyOf(new ArrayList<Product>(productsMenu.keySet()));
 	}
 	/**
 	 * Returns how much of a product is contained in this menu.

src/main/java/coreapi/OrderImpl.java

@@ -91,7 +91,7 @@ public BigDecimal totalCost()
 	 */
 	public List<Product> getProducts()
 	{
-		return Collections.unmodifiableList(new ArrayList<Product>(basket.keySet()));
+		return List.copyOf(new ArrayList<Product>(basket.keySet()));
 	}
 
 	/**
@@ -101,7 +101,7 @@ public List<Product> getProducts()
 	 */
 	public Map<Product,Integer> getBasket()
 	{
-		return Collections.unmodifiableMap(basket);
+		return Map.copyOf(basket);
 	}
 
 	/**