This book presents an interesting reading.
Since its a beginners book an explanation of what's happening in the chapter2.Utils toHex() makes sense.

can somebody explain me
1. Why everything is Hex ?
2. What's the use of data[i[ & 0xff;
3. v >> 4 ?
4. v & 0xf?

and what's the value addition this method is doing ..

Once again this is a beginners question.

Fair enough, although these are mostly Java questions.

In answer:

>1. Why everything is Hex
      it's the easiest way to represent the data, bytes of encrypted data cannot be generally represented as Strings.

>2. What's the use of data[i] & 0xff?
      bytes in Java are signed, the "& oxff" is required to make sure the resulting int is in the range 0 to 255.

>3. v >> 4
      gives the high nibble (4 bits) of the byte, indexed into digits giving the matching character.

>4. v & 0xf
      gives the low nibble of the byte, indexed into digits giving the matching character.

> what's the value addition this method is doing

Sorry, don't understand this question at all. If you're referring to the StringBuffer class append() method you can find the details in the StringBuffer JavaDoc.

Regards,

David

Thanks David for quick response.

You have written a wonderful as far as depth and coverage is concerned. Hats Off. However, it can be made easy to read by including details of some basic non common operations like the one mentioned in my query.

My further question is why bytes of encrypted data can not be represented as string. Why hexadecimal is better. Why are we using 4 bits for one Hexa character etc.

May be we can include a small intro. in the main text or a small appendix at the back.

For example I am finding it difficult to understand the use of Cipher class. You have explained Cipher class,how its created and its API. I do not understand what is Cipher providing.

That way I find Oreilly books easier to read.

I love this book, but when it comes to readability I find it confusing.

Are you planning a second edition of this book in near future.

With the use of Hex, it guarantees that the data is represented in printable characters - being a book it makes it rather difficult to print sample data otherwise.

There's no plans for a new edition at the moment.

Regards,

David