Java Programming

I would appreciate any help/advice on how to convert a hex string to an unsign int. I have the following

String hexString = "0x45 0xFF 0x09";

I need to extract the hex values from the string and convert it to an unsigned int. However, I have a problem when extracting '0xFF' - it is converted to a negative value, rather than 255.

I receive the values in String format. So I cannot change the way in which it is sent.

I would appreciate any help! Thank you in advance!