question: public static String byteArrayToHexString ( byte [ ] bytes , int pos , int len ) { StringBuilder sb = new StringBuilder ( bytes . length * 2 ) ; Formatter formatter = new Formatter ( sb ) ; for ( int i = pos ; i < pos + len ; ++ i ) { formatter . format ( "%02x" , bytes [ i ] ) ; } return sb . toString ( ) ; }
target:  Converts a byte array to hex string.