question: public static byte [ ] fromHex ( String s ) { int len = s . length ( ) ; byte [ ] data = new byte [ len / 2 ] ; for ( int i = 0 ; i < len ; i += 2 ) { data [ i / 2 ] = ( byte ) ( ( Character . digit ( s . charAt ( i ) , 16 ) << 4 ) + Character . digit ( s . charAt ( i + 1 ) , 16 ) ) ; } return data ; }
target:  Converts a hex string into an array of bytes.