/*
Apumetodeita ohjaimien väliseen kommunikaatioon ja tiedon tallentamiseen
*/
public void setBookLoanToCustomer(Book loanBook, int cardNumber){
CustomersDataAccessObject customersPersistentData = new CustomersDataAccessObject();
int index = customersPersistentData.getCustomerIndexByCardNumber(cardNumber);
this.customers.get(index).loanBook(loanBook);
ArrayList<Customer> updatedCustomers = new ArrayList<Customer>(customers);
customersPersistentData.updateAll(updatedCustomers);
customersPersistentData.save();
}