return optional list java 8 code example

Example 1: java 8 stream option

things.stream()
    .map(this::resolve)
    .filter(Optional::isPresent)
    .map(Optional::get)
    .findFirst();

Example 2: java optional to collection

public static <T> List<T> toList(Optional<T> opt) {
    return opt
            .map(Collections::singletonList)
            .orElseGet(Collections::emptyList);
}