question: public static String toHexString ( byte [ ] bytes ) { StringBuilder sb = new StringBuilder ( ) ; if ( bytes == null ) { sb . append ( "null" ) ; } else { for ( byte b : bytes ) { sb . append ( String . format ( "%02x" , b & 0xFF ) ) ; } } return sb . toString ( ) ; }
target:  Converts the specified byte array to a hexadecimal string.