Group and sum with streams

import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

record Order(String customer, int cents) {}

public class Orders {
    public static Map<String, Integer> revenueByCustomer(List<Order> orders) {
        return orders.stream()
                .collect(Collectors.groupingBy(
                        Order::customer,
                        Collectors.summingInt(Order::cents)));
    }

    public static void main(String[] args) {
        var orders = List.of(
                new Order("alice", 1200),
                new Order("bob", 800),
                new Order("alice", 300));
        System.out.println(revenueByCustomer(orders));
    }
}