How to convert hex strings to byte values in Java

Question

I have a String array. I want to convert it to byte array. I use the Java program. For example:

String str[] = {"aa", "55"}; 

convert to:

byte new[] = {(byte)0xaa, (byte)0x55}; 

What can I do?

Answer 1

String str = "Your string";  byte[] array = str.getBytes(); 

Answer 2

Looking at the sample I guess you mean that a string array is actually an array of HEX representation of bytes, don't you?

If yes, then for each string item I would do the following:

1. check that a string consists only of 2 characters
2. these chars are in '0'..'9' or 'a'..'f' interval (take their case into account as well)
3. convert each character to a corresponding number, subtracting code value of '0' or 'a'

4. build a byte value, where first char is higher bits and second char is lower ones. E.g.

   int byteVal = (firstCharNumber << 4) | secondCharNumber;