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;
}

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 ; }
converts a string of hexadecimal characters into a byte array .
