Java 8 streams - map element to pair of elements

k13i :

I have a stream of elements. I want to map each element to two different elements of the same type so that my stream will be two times longer in consequence. I did this by concatenating two streams, but I'm wondering is it possible to do this simpler? What I've done so far:

private List<String> getTranslationFilesNames() {
return Stream.concat(SUPPORTED_LANGUAGES.stream()
                .map(lang -> PATH_TO_FILES_WITH_TRANSLATIONS_1 + lang + FILE_EXTENSION),
        SUPPORTED_LANGUAGES.stream()
                .map(lang -> PATH_TO_FILES_WITH_TRANSLATIONS_2 + lang + FILE_EXTENSION))
        .collect(Collectors.toList());
}

I don't find this solution very elegant. Is there better approach to achieve the same effect?

Eran :

If you don't care about the order, you can map each element to a pair of elements with flatMap:

private List<String> getTranslationFilesNames() {
    return SUPPORTED_LANGUAGES.stream()
            .flatMap(lang -> Stream.of(PATH_TO_FILES_WITH_TRANSLATIONS_1 + lang + FILE_EXTENSION,
                                       PATH_TO_FILES_WITH_TRANSLATIONS_2 + lang + FILE_EXTENSION)),
            .collect(Collectors.toList());
}

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