int x[] = { 1, 2, 3, 4, 5 };
        int length = x.length / 2;

        IntStream right = IntStream.range(1, length + 1)
                .mapToObj(i ->  new Integer[] { -1 * i, i })
                .flatMap(Arrays::stream)
                .mapToInt(i -> x[length + i]);

        IntStream res = IntStream.concat(IntStream.of(x[length]), right);

        res.forEach(System.out::println);