public static <T> void concat(T[] sourceFirst, T[] sourceSecond, T[] dest) {
        System.arraycopy(sourceFirst, 0, dest, 0, sourceFirst.length);
        System.arraycopy(sourceSecond, 0, dest, sourceFirst.length, sourceSecond.length);
    }
@Test(expected = NullPointerException.class)
    public void concat_whenDestNull() {
        Integer[] first = new Integer[]{1, 2, 3};
        Integer[] second = new Integer[]{4};
        Integer[] concatenated = null;
        ArrayUtils.concat(first, second, concatenated);
        fail();
    }