private static void add(Map<String, MediaType> extensionToMediaType,
                            MediaType mediaType, String... extensions) {

        for (String e : extensions) {
            assert Ascii.toLowerCase(e).equals(e);
            extensionToMediaType.put(e, mediaType);
        }
    }
A map from extension to the {@link MediaType}, which is queried before
{@link URLConnection#guessContentTypeFromName(String)}, so that
important extensions are always mapped to the right {@link MediaType}.
core/src/main/java/com/linecorp/armeria/server/file/DefaultMediaTypeResolver.java