Java：十六进制转二进制后如何保证大小为2的字节数组？

Question

What I am doing :

I have a hex value string strHexVal , which I am assigning to a byte array hexBytes using DatatypeConverter.parseHexBinary(strHexVal)

What I want

The byte array hexBytes should always be of size 2 ie if after conversion the size of hexBytes is 1, I would like to insert the array with 0 and if the size after conversion is more than 2, throw an error

Can anyone help me with this?

Code:

String strHexVal= "15";
byte[] hexBytes = DatatypeConverter.parseHexBinary(strHexVal);

**Need help with this part:**
if ( hexBytes length is 1) {
   hexBytes[1] = hexBytes[0]
   hexBytes[0] = 0x00; //will this work???
}
else if (hexBytes.length > 2) {
   throw error
}

Answer 1

No, you can't just do hexBytes[0] = 0x00; because Java arrays have a fixed size once they are created.

You have to create a new byte[] :

if ( hexBytes.length == 1) {
    hexBytes = new byte[] { 0, hexBytes[0] };
}

Make sure you decide what to do if hexBytes.length is 0 as well. This will be the case if the input string is empty.