How to get the filled field of java.util.Set <Object> or if the field is empty, return something else?

I have an Addresses class that is used in two attributes of the Customer class, the first attribute is a simple object to represent the customer's default address and another attribute is a Set <> of addresses that the customer can have.

I need to send the postalCode field to another class. I would like to check in Set <> if there is a filled postalCode, if yes, send this value, otherwise (if there is no filled postalCode within Set <>) then I should send the postalCode value from the default address. How to do this? I tried this way before:

Optional.ofNullable(Stream.of(product.getCustomer().getAddresses()).forEach
(i -> i.getPostalCode())).orElse(product.getCustomer().getAddressDefault().getPostalCode()))

My classes bellow:

public class Customer {
	private Addresses addressDefault;
	private Set<Addresses> addresses;
}
public class Addresses {
	private String postalCode;
	private String city;
	private String state;
	private String country;
}

Using Java 8 streams, you can use map to transform an address to its postalCode, use filter to remove null values, and use findFirst to get the first non-null postalCode.

Stream.findFirst deals with empty streams by returning an optional. To get its value or a default value, use the Optional.orElse method.

In code:

String postalCode = customer.addresses.stream()
        .map(addresses -> addresses.postalCode)
        .filter(Objects::nonNull)
        .findFirst()
        .orElse(customer.addressDefault.postalCode);