Question

I would like to know if there any difference between Java byte code and .NET byte code? If there any difference, shall I take hexadecimal values of that Java byte code and .Net byte code. Because, hexadecimal is independent of languages and it is universal specification.

Problem description

We are developing a mobile application in j2me and Java. Here I am using external finger print reader for reading/verifying finger print. We are using one Java api for reading/verifying finger print.

I capture the finger template and raw image bytes. I convert the raw image bytes into hex form and stored in a separate text file.

Here we using a conversion tool (developed in .NET) that converts the hex form into image. With the help of that tool we are trying to get the image from that text file. But we cannot get the image correctly.

The .NET programmer says the Java byte and .NET byte differ. Java byte ranges from -128 to 127. But .NET byte ranges from 0 to 255. So there is a problem.

But my assumption here is: the hex is independent of Java & .net. It is common to both. So, instead of storing byte code in text file, I plan to convert that byte code into hexadecimal format. So,our .NET conversion tool automatically convert this hexadecimal into Image.

I don’t know whether I am going on correct path or not?

Answer 1

I capture the finger template and raw image bytes .I convert the raw image bytes into hex form and stored in a separate text file.

OK; note, storing as binary would have been easier (and more efficient), but that should work

Here we using a conversion tool (developed in .NET) that converts the hex form into image.With the help of that tool we are trying to get the image from that text file.But we cannot get the image correctly.

Rather than worrying about the image, the first thing to do is check where the problem is; there are two obvious scenarios:

• you aren’t reading the data back into the same bytes
• you have the right bytes, but you can’t get it to load as an image

First; figure out which of those it is, simply by storing some known data and attempting to read it back at the other end.

The .NET programmer says the java byte and .NET byte differ.Java byte ranges from -128 to 127.But .NET byte ranges from 0 to 255.So there is a problem.

That shouldn’t be a problem for any well-written hex-encode. I would expect a single java byte to correctly write a single hex value between 00 and FF.

I dont know, whether i am going on Correct path or not?

Personally, I suspect you are misunderstanding the problem, which makes it likely that the solution is off the mark. If you want to make life easier, store as binary rather than text; but there is no inherent problem exchanging hex around. If I had to pack raw binary data into a text file, personally I’d probably go for base-64 rather than hex (it will be shorter), but either is fine.

As I mentioned above: first figure out whether the problem is in reading the bytes, vs processing the bytes into an image. I’m also making the assumption that the bytes here are an image format that both environments can process, and not (for example) a custom serialization format.