public static String s1(int v) {
        char[] result = new char[3];

        if (v < 0) {
            result[0] = '-';
            v = -v;
        } else {
            result[0] = '+';
        }

        for (int i = 0; i < 2; i++) {
            result[2 - i] = Character.forDigit(v & 0x0f, 16);
            v >>= 4;
        }

        return new String(result);
    }
@Test
    public void testS1() {
        Assert.assertEquals("+00", Hex.s1(0));
        Assert.assertEquals("-00", Hex.s1(-2147483648));
        Assert.assertEquals("+7b", Hex.s1(123));
        Assert.assertEquals("+d2", Hex.s1(1234567890));
    }