Chaining Optionals in Java 8

Question

Looking for a way to chain optionals so that the first one that is present is returned. If none are present Optional.empty() should be returned.

Assumi

Answer 1

Maybe one of

    public  Optional firstOf(Optional first, @SuppressWarnings("unchecked") Supplier>... supp) {
        if (first.isPresent()) return first;
        for (Supplier> sup : supp) {
            Optional opt = sup.get();
            if (opt.isPresent()) {
                return opt;
            }
        }
        return Optional.empty();
    }

    public  Optional firstOf(Optional first, Stream>> supp) {
        if (first.isPresent()) return first;
        Stream> present = supp.map(Supplier::get).filter(Optional::isPresent);
        return present.findFirst().orElseGet(Optional::empty);
    }

will do.

The first one iterates over an array of suppliers. The first non-empty Optional<> is returned. If we don't find one, we return an empty Optional.

The second one does the same with a Stream of Suppliers which is traversed, each one asked (lazily) for their value, which is then filtered for empty Optionals. The first non-empty one is returned, or if no such exists, an empty one.