public static long toLong(String value) {
        String[] octets = value.split(":");
        if (octets.length > 8) {
            throw new NumberFormatException("Input string is too big to fit in long: " + value);
        }
        long l = 0;
        for (String octet: octets) {
            if (octet.length() > 2) {
                throw new NumberFormatException(
                        "Each colon-separated byte component must consist of 1 or 2 hex digits: " + value);
            }
            short s = Short.parseShort(octet, 16);
            l = (l << 8) + s;
        }
        return l;
    }
@Test(expected = NumberFormatException.class)
    public void testToLongError() {
        String dpidStr = "09:08:07:06:05:04:03:02:01";
        HexString.toLong(dpidStr);
        fail("HexString.toLong() should have thrown a NumberFormatException");
    }