question: private static byte [ ] fromHex ( String hex ) { byte [ ] binary = new byte [ hex . length ( ) / 2 ] ; for ( int i = 0 ; i < binary . length ; i ++ ) { binary [ i ] = ( byte ) Integer . parseInt ( hex . substring ( 2 * i , 2 * i + 2 ) , 16 ) ; } return binary ; }
target:  Converts a string of hexadecimal characters into a byte array.