How to locate & write to files inside a Jar

[Andrei Antonescu]

Hello,
I have a simple program that reads a string from a file. I want to pack it as a Jar so I need to locate the input file in the following way:

   
InputStream in=getClass().getResourceAsStream("resources/textfile");  
BufferedReader br=new BufferedReader(new InputStreamReader(in));

This code works but how can I write to a file located in the same Jar? (the getResourceAsStream returns an InputStream, not the OutputStream that I need).

Thanks in advance,

[pete stein]

Jars don't have files but rather resources, and you really shouldn't be trying to write into them. Instead perhaps use properties or a datafile external to the Jar.

[Stephan van Hulst]

I echo that you shouldn't write to a Jar file.

That said, you can. A jar file is simply a zip file with a different extension. You can edit the files in a roundabout way using java.util.zip.*.

[Rob Spoor]

No you can't. Editing into a ZipFile is not supported, not even by the zip protocol itself. If you replace a file inside the zip file, changing the size, you will need to shift data inside the entire zip file.

Most programs that do allow changing files inside a zip file use a shadow copy - upon committing the changes the all contents are put into a new zip file; afterwards the old zip file is replaced by the new one.