Stream of optional fields return values

Question

I have a few Optional fields with String and Long values:

Optional<Long> id;
Optional<String> name;
Optional<String> lastname;
Optional<Long> number;
....

I would like to return List with contains all of the values. If e.g optional "name" is no present, should be stored empty String. Result of method should be List with values e.q: "1", "John", "", "5".

I made stream:

Stream fields = Stream.of(id, name, lastname, number);

But I have no idea what next.

Regards.

Answer 1

You can use:

List<String> list = Stream.of(id, name, lastname, number)
        .map(op -> op.map(o -> o.toString()).orElse(""))
        .collect(Collectors.toList());

On each optional in stream you will map it into it's String version using toString() from Object class and for null you will map it into empty String. Than, you will collect it into list.