How to match a certain hex value in a file JAVA?

Question

I need to be able to find a certain value (such as 80) in a file like:

4D 54 68 64 00 00 00 06 00 01 00 01 00 C0 4D 54 72 6B 00 00 00 31 00 90 60 40 81 40 80 60 40 00 90 62 40 81 40 80 62 40 00 90 64 40 81 40 80 64 40 00 90 62 40 81 40 80 62 40 00 90 57 40 81 40 80 57 40 00 FF 2F 00

example of my code :

RandomAccessFile file = new RandomAccessFile(new File(fichierAConvertir), "rw");

        System.out.println(fichierAConvertir);
        if(file.read() == 0x80)
        {
            System.out.println("trouvé");
        }
        else{
            System.out.println("pas trouvé");
        }

I also want to be able to replace all cases of that value by an another value .

I'm French, so sorry for my English skills..

You need me to find 80 in a file? I think you need to write some code yourself to find it. Show some effort and you will receive help. — Kallja, Jan 27 '14 at 15:31
yes. I'm a begginer and i'm stuck about this i tried with regex but doesn't work.. i know how to do for non hex value . @Kallja — Clyx, Jan 27 '14 at 15:34
Then post your code (only relevant bits, but complete and compiling) and possible stack traces and let's see what's wrong with it. The idea of this sit isn't provide complete solutions for problems but the help you find one for yourself. @Clyx — Kallja, Jan 27 '14 at 15:39
if you don't want to use regex, try with the Scanner class, it's simpler for a beginner http://stackoverflow.com/questions/11871520/how-to-use-the-scanner-class-in-java — Alessio, Jan 27 '14 at 15:43
@Kalija It doesn't have to ***always*** compile if compiling is the issue that needs to be resolved. |=^/ — But I'm Not A Wrapper Class, Jan 27 '14 at 15:43

score 0 · Answer 1 · edited May 23 '17 at 12:21

0

You could easily read the file into a String, then do a replace all on that String. Finally, write that updated String back into the file. You can read the file into a String (found here):

Scanner scanner = new Scanner(new File("filename"));
String content = scanner.useDelimiter("\\Z").next();
scanner.close();

There are alternative ways to have a File turn to a String in these two links:

Choose one of these 3 methods, then continue with the following code.

There is a replaceAll() method for String in the API:

content = content.replaceAll("80", "some other string");

Finally, write this update String back into the file as so:

PrintWriter writer = new PrintWriter("filename", "UTF-8");
writer.println(content);
writer.close();//don't forget to close!

If you want to be able to convert String to hex and back, then I'd check out this question.

NOTE: Don't forget to close your writer/scanner/printer/etc. Check out this solution as to why.

edited May 23 '17 at 12:21

Community

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answered Jan 27 '14 at 16:03

But I'm Not A Wrapper Class

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thanks to answer ! I get "java.util.NoSuchElementException". I replaced "some other string" by "90".. @Mohammad S. – Clyx Jan 28 '14 at 16:11
Does that file name exist? Is it empty? – But I'm Not A Wrapper Class Jan 28 '14 at 16:47
i also have a method that return the file ;) no my file is not empty :s @Mohammad S. – Clyx Jan 28 '14 at 16:47
See that yellow swiggly line at the `String content = new Scanner(...` line? What is that warning saying? I suspect the String `fichierAConvertir` is empty, null, or incorrect. – But I'm Not A Wrapper Class Jan 28 '14 at 16:50
is just to add "@SupressWarnings 'ressource' to 'content'.. @Mohammad S. – Clyx Jan 28 '14 at 16:52
Before creating that `Scanner`, print out the value of `fichierAConvertir`. What does it print? Also, which exact line is this error from? – But I'm Not A Wrapper Class Jan 28 '14 at 16:57
it print the good path :s , It's not so easy to read a hex file ^^ the line error is the same in the screenshot @Mohammad S. – Clyx Jan 28 '14 at 17:00
I updated the answer, but I don't think that's your issue. However, can you tell me where the stack trace says that Exception is from? Which exact line? Have you used a debugger? – But I'm Not A Wrapper Class Jan 28 '14 at 17:04
I dont know how to know the stacktrace says ..:s the debug mod didnt say anything @Mohammad S. – Clyx Jan 28 '14 at 17:14
It should automatically print in your Console – But I'm Not A Wrapper Class Jan 28 '14 at 17:18
There is two things I can think of. Do you have any other scanner/printer/etc accessing this file at the moment or another process accessing this file? If so, this Exception will be thrown. Another issue is the way we convert the file to a String. I will update an alternative method. – But I'm Not A Wrapper Class Jan 28 '14 at 17:39
Also check this out: http://stackoverflow.com/questions/15443383/scanner-nosuchelementexception – But I'm Not A Wrapper Class Jan 28 '14 at 17:43
I use myfile.toString(); and it works see my new methos i get nullPointerException : http://s22.postimg.org/5hhv07c01/classes.jpg this my 2 classes @Mohammad S. – Clyx Jan 28 '14 at 17:51
Post a screenshot of the stacktrace instead – But I'm Not A Wrapper Class Jan 28 '14 at 18:24
http://postimg.org/image/sjd3w6skh/ Thank you again to spend some time with me. @Mohammad S. – Clyx Jan 28 '14 at 18:29
not really i added the "byte" .. i test all i can ^^ but always doesn't work ! @Mohammad S. – Clyx Jan 28 '14 at 18:38
We could use the chat feature on Stackoverflow, but that's all I can do from here. |=^/ – But I'm Not A Wrapper Class Jan 28 '14 at 18:49
So we can try but can you start the chat because I don't know how to proceed. @Mohammad S. – Clyx Jan 28 '14 at 18:53

How to match a certain hex value in a file JAVA?

1 Answers1