Challenge: Calculating Total Cost with Discounts and Tax
Tarefa
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Implement a shopping cart system that calculates the total order cost, applying a discount and sales tax based on predefined conditions.
- Use
map()to get the total price of each product (there is a dedicated methodgetTotalPrice()in theProductclass). - Apply
reduce()to sum up all product prices. - Use a ternary operator to check if the
subtotalexceeds the discount threshold (DISCOUNT_THRESHOLD) and calculate thediscount. Ifsubtotalis greater than the threshold, apply a 10% discount (DISCOUNT_PERCENTAGE); otherwise, set the discount to 0.0. - Determine the discount amount by multiplying
subtotalbyDISCOUNT_PERCENTAGE. - Calculate the pre-tax amount (
preTaxAmount) by subtractingdiscountfromsubtotal. - Compute the sales tax (
tax) by multiplyingpreTaxAmountby the sales tax rate (SALES_TAX). - Return the final total, calculated as
preTaxAmount + tax.
Solução
solution
package com.example;
import java.util.Arrays;
import java.util.List;
public class Main {
public static void main(String[] args) {
ShoppingCart cart = new ShoppingCart(Arrays.asList(
new Product("Laptop", 1200.0, 1),
new Product("Wireless Headphones", 150.0, 2),
new Product("Smartphone", 800.0, 1),
new Product("Charging Cable", 25.0, 3),
new Product("Tablet", 600.0, 1),
new Product("Mechanical Keyboard", 200.0, 1),
new Product("Gaming Mouse", 100.0, 1)
));
System.out.println("Subtotal: $" + cart.calculateSubtotal());
System.out.println("Total (after tax & discount): $" + cart.calculateTotal());
}
}
class ShoppingCart {
private List<Product> products;
private static final double SALES_TAX = 0.08; // 8% sales tax
private static final double DISCOUNT_THRESHOLD = 1000.0;
private static final double DISCOUNT_PERCENTAGE = 0.10; // 10% discount
public ShoppingCart(List<Product> products) {
this.products = products;
}
public double calculateSubtotal() {
return products.stream()
.map(Product::getTotalPrice)
.reduce(0.0, Double::sum);
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Seção 3. Capítulo 7
package com.example;
import java.util.Arrays;
import java.util.List;
public class Main {
public static void main(String[] args) {
ShoppingCart cart = new ShoppingCart(Arrays.asList(
new Product("Laptop", 1200.0, 1),
new Product("Wireless Headphones", 150.0, 2),
new Product("Smartphone", 800.0, 1),
new Product("Charging Cable", 25.0, 3),
new Product("Tablet", 600.0, 1),
new Product("Mechanical Keyboard", 200.0, 1),
new Product("Gaming Mouse", 100.0, 1)
));
System.out.println("Subtotal: $" + cart.calculateSubtotal());
System.out.println("Total (after tax & discount): $" + cart.calculateTotal());
}
}
class ShoppingCart {
private List<Product> products;
private static final double SALES_TAX = 0.08; // 8% sales tax
private static final double DISCOUNT_THRESHOLD = 1000.0;
private static final double DISCOUNT_PERCENTAGE = 0.10; // 10% discount
public ShoppingCart(List<Product> products) {
this.products = products;
}
public double calculateSubtotal() {
return products.stream()
.map(___)
.reduce(___, ___);
}
public double calculateTotal() {
double subtotal = calculateSubtotal();
double discount = (subtotal > ___) ? subtotal * ___ : 0.0;
double preTaxAmount = ___;
double tax = ___
return ___;
}
}
class Product {
private String name;
private double price;
private int quantity;
public Product(String name, double price, int quantity) {
this.name = name;
this.price = price;
this.quantity = quantity;
}
public double getTotalPrice() {
