client.java

public class Client {
  
  public Client(CustomerRepository customerRepo, OrderRepository orderRepo) {
    this.customerRepo = customerRepo;
    this.orderRepo = orderRepo;
  }
  
  public void demonstrate() {
    customerRepo.allCustomers().forEach(customer -> {
      List<Order> orders = orderRepo.getOrdersForCustomer(customer.getId());
      //display orders...
    });
   }
}