question: public static String convertToHexString ( byte [ ] bytes ) { int size = bytes . length ; StringBuffer buffer = new StringBuffer ( size * 2 ) ; for ( int i = 0 ; i < size ; i ++ ) { int x = bytes [ i ] ; if ( x < 0 ) x += 256 ; String tmp = Integer . toHexString ( x ) ; if ( tmp . length ( ) == 1 ) buffer . append ( "0" ) ; buffer . append ( tmp ) ; } return buffer . toString ( ) ; }
target:  Convert Byte Array to Hex String