question: public static byte [ ] hexStringToBytes ( String hexString ) { byte [ ] data = new byte [ hexString . length ( ) / 2 ] ; for ( int i = 0 ; i < data . length ; i ++ ) { String a = hexString . substring ( i * 2 , i * 2 + 2 ) ; data [ i ] = ( byte ) Integer . parseInt ( a , 16 ) ; } return data ; }
target:  Converts a string of hex characters to a byte array.