public static String encodeAsString(byte ... bytes) {
        if (bytes == null)
            return null;
        return bytes.length == 0 ? "" : CodecUtils.toStringDirect(codec.encode(bytes));
    }
Returns a base 16 encoded string (in upper case) of the given bytes.
aws-java-sdk-core/src/main/java/com/amazonaws/util/Base16.java