public static byte[] fromHex(String hex) {
        Preconditions.checkArgument(hex.length() % 2 == 0, "length must be a multiple of 2");
        int len = hex.length();
        byte[] b = new byte[len / 2];
        for (int i = 0; i < len; i += 2) {
            b[i / 2] = hexCharsToByte(hex.charAt(i), hex.charAt(i + 1));
        }
        return b;
    }
Create a byte array from a string of hash digits. The length of the string must be a multiple
of 2
stroom-bytebuffer/src/main/java/stroom/bytebuffer/hbase/Bytes.java